Get Values between Two Dates using SQL BETWEEN

Let’s say you have a requirement to get all values between two date ranges or specific date time ranges. You can use SQL BETWEEN operator to get this done. Here is the example to get all values between date 19th March 2021 and 20th March 2021. Below example is also an use case of how to use BETWEEN operator in WHERE clause. You can remove ‘-‘ from date ranges if you want and you can directly mention date ranges as ‘20210319’ AND ‘20210320’.

SELECT name, type_desc,create_date, modify_date
FROM sys.objects
WHERE modify_date BETWEEN ‘2021-03-19’ AND ‘2021-03-20’

Here, i have fetched all modified objects on my SQL Server between given date range. Here is the output. We can see there are more than 730 rows returned. You can compare the dates in modify_date column whether output has returned correct data or not.

Now, Next requirement could be to retrieve some data between two date time ranges like you want details between specific time of dates. I will take same above query to show case this example as well. When we don’t specify the time along with date range then it defaults to 12:00 A.M. 

SELECT name, type_desc,create_date, modify_date
FROM sys.objects
WHERE modify_date BETWEEN ‘2021-03-19 4:38:00’ AND ‘2021-03-19 4:38:30’

Here, i have retrieved all modified objects between 30 seconds of above given time (Time 4:38:00 to 4:38:30). Here is the output and it is showing only 35 rows.

You can use this SQL between two date ranges or datetime ranges to fetch your data. You can use this operator in INSERT, UPDATE or DELETE statements as well.

Get Values between Two Numbers

This section will explain about getting details between two number ranges. Let me take same table which we have taken for above section sys.objects. Now, i want to get all objects having object id between 25 to 30 or you can mention any range. This is just an example to showcase. These number ranges will change as per your need and nature of data.

SELECT name, object_id, type_desc, create_date
FROM sys.objects
WHERE object_id BETWEEN ’25’ AND ’30’

Note, above object_id is column name and not the T-SQL function. Have a look at its output in below image. We have got only rows which are assigned with these object ids.

Use BETWEEN with NOT Operator

Above all examples shows how to get data between two ranges but we can use NOT operator with BETWEEN to return all values which is not between specified two ranges. Let’s take above example where BETWEEN operator has returned only 5 rows based on their specified two ranges. Now if i will use NOT operator in above T-SQL statement then output will return all rows of table sys.objects except above 4 rows which will be prevented by NOT operator. Let me show you this example.

SELECT name, object_id, type_desc, create_date
FROM sys.objects
WHERE object_id NOT BETWEEN ’25’ AND ’30’

Have a look at below highlighted are where objects ids between 25 to 30 are missing.

Here, i have shown you few use cases of SQL Server T-SQL operator BETWEEN statement. You can go head and try this operator for your business needs. For more information on this operator, visit MSDN article.

Read More

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• SQL Server Interview Questions & Answers on Indexes

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• If you have changed database server name then we should change SQL Server Instance name as well.
• If you have cloned a database server from DBSERVER1 to DBSERVER2. Here, SQL Server installed on DBSERVER1 will be copied with same name to DBSERVER2. You need to change the SQL Server instance name on DBSERVER2.
• Naming convention is not met.

Please keep in mind that we cannot change complete name of SQL Server named instance. Suppose you have installed a named instance SERVERNAME\DBInstance1 on your server. If you want to rename this named instance then we can only change first part of this name i.e. SERVERNAME. You cannot change DBInstance1 so your named instance will look like DBSERVERNAME\DBInstance1 post name change.

Impact of Changing SQL Server Instance Name

We need to plan carefully before renaming any SQL Server Instance. Below is the list of possible impacts that you should go through while renaming SQL Server Instance name.

• Those domain users who are accessing or connecting to the SQL Server Instance as part of Windows group will not be able to connect to renamed instance of SQL Server. Make sure to update the Windows group to specify the new computer name to establish connectivity to the SQL Server instance.
• You would not be able to access reporting services after renaming the instance name. You should follow steps mentioned in attached article to rename SQL Server instance that is running with reporting services.
• If you have database mirroring on the SQL Server instance then you need to drop the mirroring and then reconfigure it post renaming the SQL Server Instance.
• Renaming SQL Server instance name does not support if your instance has replication, except when you use log shipping with replication.
• You can change the name of SQL Server instance on secondary server in log shipping if the primary server is permanently lost.
• If you have linked server configurations then it will be affected by the computer renaming operation. Use sp_addlinkedserveror sp_setnetname to update computer name references.

Rename SQL Server Instance

SQL Server instance name along with other system metadata stores in sys.servers system object. We need to update details in system metadata to reflect new name. Also i would suggest to not change SQL Server Instance name directly on your production server.

Suppose you have installed default instance of SQL Server in your database server. If you have changed the name of your database server then you need to update the name of default SQL Server instance as well in sys.servers system table. First, we need to drop the existing SQL Server instance name then we will add new name as per our choice. Follow below steps to change SQL Server instance name.

--Drop existing name
sp_dropserver [old_Instance_name]; 
GO 

--Update New name
sp_addserver [new_Instance_name], local; 
GO

If you have installed a named instance on your database server then you can run below command to change SQL Server Instance name.

sp_dropserver [old_name\instancename]; 
GO 

sp_addserver [new_name\instancename], local; 
GO

Note: Make sure to restart SQL Server services post running above commands to reflect these changes.

You can verify the changes by running below commands or by querying sys.servers system table. If you have not restarted SQL Server services then you might be getting older SQL Server instance name. So restart SQL Server service to apply new changes.

SELECT @@SERVERNAME

If you have remote logins on your database server then you might get error 15190 while running sp_dropserver command. Read below article to fix this issue and then proceed with the instance name change.

• Fix Error 15190: There are still remote logins for the server

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• Configure Reporting Services After Renaming SQL Server Instance Name
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• Find all trace profilers running on SQL Server Instance
• How to Move a Table to Another Filegroup?

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Server: Msg 15190, Level 16, State 1, Procedure sp_dropserver
There are still remote logins for the server ‘DBSERVER’.

Error 15190 – Root Cause

As we know we need to first drop the existing details of SQL Server instance name from metadata system table sys.servers and then add new instance name in order to change the instance name. I was doing the same and running below command to drop the old instance name.

sp_dropserver <old_Name>; 
GO

I had received this error 15190 while executing above command and that is because of some remote logins present of the SQL Server instance.

If your database server has any remote login that you use for linked servers or some other purposes then you will get such issues. We need to drop all the remote logins to fix this issue and execute above command successfully.

Solution

To fix this issue we need to identify remote logins and drop them before changing the SQL Server instance name. We will be using a system stored procedure sp_dropremotelogin to drop all remote logins from our SQL Server instance. Run below command to drop all remote logins from a default instance of SQL Server.

sp_dropremotelogin old_name; 
GO

If you have named instance running on your database server then you can run below command. Make sure to change the name of server in place of Old_DBSERVER\Instancename.

sp_dropremotelogin Old_DBSERVER\Instancename; 
GO

Once all remote logins have been dropped you can go ahead and perform your SQL Server Instance name change operation. Make sure to create remote logins for your linked servers or alias post changing the instance name.

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Read More:

• How to Change SQL Server Instance Name?
• How to Rename SQL Server Instance that is running with SQL Server Reporting Services?
• Fix Error 15434: Could not drop login “domain\loginname” as the user is currently logged in
• Fix Error 15174: Login owns one or more databases. Change the owner of database before dropping the login.
• How to Change Hostname of RHEL system?

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Let’s start with the basics. MSDN says “Trace flags are used to temporarily set specific server characteristics or to switch off a particular behavior. Trace flags are frequently used to diagnose performance issues or to debug stored procedures or complex computer systems.”

There are two types of trace flags in SQL Server.

• Session
• Global

We can enable trace flag for the context of a specific query that we can run under a session. Session trace flags can be enabled for a connection and are visible only to that connection. This type of trace flag never affects another session running on your database server and the effect of the trace flag is lost when that connection logs out.

Global trace flags are set at the server level and must be enabled globally. If you will try to enable global trace flag for a particular session then there will not be any impact of this trace flag. Let’s go ahead and understand how we can check the status of trace flags running on your SQL Server instance.

Check Trace Flag Status

We use DBCC TRACESTATUS command to check all running or active trace flags on database system. We can also check the status of a specific trace flag using this DBCC command. The output of this DBCC command has four columns. First column is the trace flag number, second column shows the status of trace flag, third and fourth columns are showing whether the trace flag is enabled at the global level or session level.

The status column of this DBCC command has two values. The value shows whether the trace flag is ON (1) or OFF (0). You can see the below screenshot to understand the trace flags and their status.

DBCC TRACESTATUS

We can run above DBCC command in different ways to get distinct outputs about trace flags status. Here, I am giving you few examples to use DBCC TRACESTATUS command.

Run below command to display the status of all trace flags that are currently enabled globally.

DBCC TRACESTATUS(-1);  
GO

We can even get status of multiple specific trace flags by executing below command. Run below command to get the status of trace flags 8690 and 1118.

DBCC TRACESTATUS (8690, 1118);  
GO

If you want to list all the trace flags that are enabled for the current session then you can get it by running below command.

DBCC TRACESTATUS();  
GO

If you want to check whether trace flag status for specific trace is enabled globally or not then you can run below command.

DBCC TRACESTATUS(8690, -1)

Enable Trace Flag

We enable trace flags to gather more information about certain logs during some transactions. We use DBCC TRACEON command to enable SQL Server trace flags. Here, I will show you different uses of DBCC TRACEON command to enable trace flags.

Remember, all trace flags enabled using DBCC TRACEON command will be disabled once you restart the SQL Server service. If you want to enable any trace flag permanently then we recommend that you should enable them at startup, by using the -T command line option. This ensures the trace flag remains active after a server restart. You can launch SQL Server Configuration Manager and open the Properties window of SQL Server service. Here you can click on Startup Parameters tab. Here you can add your trace flag number along with -T and then click on Ok button to close the window.

If we need to enable a trace flag globally then we need to run below command with -1 option as shown in below screenshot.

DBCC TRACEON (8690, -1)

Now we can check the trace flag status whether it’s been enabled globally on our database system or not.

If you want this trace to be enabled for current connection only then you should run below command. You can remove -1 from above command.

DBCC TRACEON (8690);  
GO

Even you can enable multiple trace flags by running single command. You can run below command to enable trace flag 8690 and 1117 globally. If you want to enable it for current connection only then you can remove -1 from below command.

DBCC TRACEON (8690, 1117, -1);  
GO

Run below DBCC command to check the status of the trace flag that we have enabled by running above command.

DBCC TRACESTATUS

You can see trace flag 8690 is showing along with its value set as 1 for session as well as global in below screenshot.

If you want to check trace flag status for specific trace number then you can run below command. Below command will let you know whether trace flag 8690 is enabled globally or not.

DBCC TRACESTATUS(8690, -1)

Disable Trace Flag

Similarly, we can disable trace flag 8690 that we have enabled in above section by executing another DBCC command known as DBCC TRACEOFF. Run below command to disable trace flag. If we will use -1 value along with DBCC TRACEOFF command that means it will disable this trace flag globally.

DBCC TRACEOFF(8690, -1)

If you want to disable it for current connection only then we will remove -1 from above command and run below command.

DBCC TRACEOFF(8690);   
GO

Now we can again check the status of trace flag 8690 whether this trace is still active or it has been deactivated by above command.

DBCC TRACESTATUS

We can see trace 8690 is disabled now and this trace flag cannot be active in below image.

If you want to check trace flag status for a individual trace then you can run below command.

DBCC TRACESTATUS(8690, -1)

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Read More:

• Find Total no of Running Traces files on your Database Server
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There are four new T-SQL functions introduced in SQL Server 2017. These are very useful that make SQL Server developers life easier. Let’s have a look at each one of these SQL 2017 new  functions with their examples and use cases.

CONCAT_WS

If you look at the name of this function CONCAT_WS then it will come out as concatenate with separator. This function requires a separator specified as 1^st argument and minimum of two or more arguments mentioned as remaining arguments. All arguments will be concatenated into a single string with a separator specified in the 1st argument. Null values are ignored during concatenation, and does not add the separator.

Below are the examples of this new function. Suppose, you want to gather login details that has sysadmin access on your SQL Server Instance in a separator format then you can use below command to get these details. You can change the columns of this command or you can also change the T-SQL command if you want to gather some other information. You can also change the separator comma mentioned in first argument to some other separator as per your wish.

SELECT CONCAT_WS (‘,’, name, status, sysadmin) As LoginDetails from syslogins

The output of above command will look like below details.

LoginDetails

Sa,9,1
techyaz\test1,10,1
techyaz\deo1,9,0
ty1,9,0

As I said above, this function skips the null values. You can see this by running below command on your SQL Server 2017 instance.

SELECT CONCAT_WS(',',132, NULL, NULL, 'Urban Estate', 'Gurgaon', 122001) AS Address; 

Output of above command will be:

Address

132,Urban Estate, Gurgaon, 122001

You can see null values have been skipped in above output.

TRANSLATE

Another useful T-SQL function introduced in SQL Server 2017 is TRANSLATE. This function returns a string given in first argument after some characters given in second argument translated with the characters given in third arguments.

Here, you need to give three inputs. Input string is first argument that we want to modify with some changes. Second Argument is characters that is an expression of any character type containing characters that should be replaced. Third argument is an expression that will replace second argument mentioned in Inputstring. Make sure that the length and type of characters and translations will be same otherwise you will end up with errors. The output will be same as given in input string if you pass NULL value in any of the second or third argument.

Below is the example of this function.

SELECT TRANSLATE ('[7.124, 9.6]' , '[,]', '( )') AS Values,

Here we are replacing a square bracket having comma with regular bracket and blank space in place of comma.   Output of above T-SQL will be given below.

Values

(7.124 9.6)

You can see square bracket has been replaced with the given one and comma separator is also removed from above expression. If you want to revert it of you want to enter comma or any separator with changing the give brackets you can also get this done using this function.

SELECT TRANSLATE('(7.124 9.6)' , '( )', '[,]') AS Values;

Output of above command will look like below information.

Values

[7.124,9.6]

Another example of this function is given below. Run below t-sql command if you want to replace few to the brackets with the given in transactions argument.

SELECT TRANSLATE('[4+2]/{6-2}', '[]{}', '()()') As Formula;

The output of above command will be look like below info.

Formula

(4+2)/(6-2)

TRIM

This function has enabled users to remove the space characters or other characters from the start or end of the string. Earlier we used to do the same thing using LTRIM(RTRIM(@string)) T-SQL command.

Below example will remove the free spaces given before and after the word techyaz.

SELECT TRIM( '             techyaz              ') AS Result;

We can the output of above t-sql function given as:

Techyaz

Earlier we used to do the same thing using below t-sql command.

LTRIM(RTRIM('    techyaz    '))

STRING_AGG

Many developers were expected this function to be part of SQL Server since long time. Now their wish have been completed in SQL Server 2017. STRING_AGG is going to become very popular among all new functions. This function concatenates the values of string expressions and places separator values between them. The separator is not added at the end of string.

STRING_AGG is an aggregate function that takes all expressions from rows and concatenates them into a single string. Here is the example where we will see output from a table in a given format.

SELECT STRING_AGG(CONCAT(FirstName, ' ', LastName, ' (', ModifiedDate, ')'), CHAR(13))
AS names
FROM Person.Person;

Output of above command will look like:

Names

Manvendra Singh (Feb 8 2018 12:00AM)
Maruti Nandan (Dec 24 2017 12:00AM)
Angelo M (Feb 5 2018 12:00AM)

You can see all column values are showing a single string in each row. Another aspect of this function is given in below example.

Suppose, you have a database having information about your blog or published articles. There are separate tables to save articles and their tags. Now, developers want to return one row per each article with all associated tags. We can use below query to get the output.

SELECT a.ArticleId, Title, STRING_AGG (tag, ',') as Tags
FROM dbo.Article AS a
LEFT JOIN dbo.ArticleTag AS t
ON a.ArticleId = t.ArticleId
GROUP BY a.articleId, title;

Output of above command will look like below details.

Here, I have described new T-SQL functions introduced in SQL Server 2017 with their examples. I hope you like this article. Please follow our Facebook page and Twitter handle to get latest updates.

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There is new feature called Resumable Online Index Rebuild introduced in SQL Server 2017 that is an extension of online index rebuild operation. Learn about Resumable Online Index Rebuild operation in SQL Server 2017 in attached article.

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ONLINE Index Rebuild Operation

Rebuilding an index drops and re-creates the index. Indexes becomes unavailable during this exercise that causes an outage for that object. Microsoft has given a solution to avoid inaccessibility of the object during index rebuild operation. We can specify ONLINE keyword value as ON in CREATE INDEX or ALTER INDEX to rebuild indexes online.

When you are rebuilding an index and the ONLINE option is set to ON, the underlying objects, the tables and associated indexes, are available for queries and data modification. Row versioning is used to allow for transactional consistency. SQL Server reindex ONLINE option does not work if your table has BLOB data types or index is an XML index or Spatial index.

I have given the list of T-SQL statements that will rebuild indexes ONLINE on your table. You just need to change the index name, table name and column name from below statements.

Below SQL code will rebuild the clustered index on column EMPID on the table dbo.Salary. As we are rebuilding this cluster index using dropping and recreating the cluster indexes so existing index will be dropped in the process, but it will be available during the operation because the ONLINE option is specified.

CREATE CLUSTERED INDEX CI_Salary_EMPID ON dbo.Salary(EMPID)
WITH(DROP_EXISTING = ON, ONLINE = ON)

We can also use ALTER INDEX statement to rebuild a specific index or all indexes on a specified table. The ONLINE syntax remains the same as the CREATE INDEX statement if you want to run this operation online.

ALTER INDEX ALL ON [dbo.Salary]
REBUILD WITH(ONLINE = ON)

Above statement will rebuild all indexes on table Salary keeping everything accessible during this operation. Now, we can also rebuild clustered index only on the dbo.Salary table. The ONLINE option is specified, which means that the table will be accessible during the rebuild operation.

ALTER INDEX CI_Salary_EMPID ON dbo.salary
REBUILD WITH(ONLINE = ON)

But if we will remove ONLINE option from above statement, then table will NOT be accessible during rebuild operation. You can run below command to validate the accessibility of your table for which you are rebuilding the indexes.

ALTER INDEX CI_Salary_EMPID ON dbo.salary
REBUILD

Disk Space Considerations 

Disk space is an important consideration when you create, rebuild, or drop indexes. Inadequate disk space can degrade performance or even cause the index operation to fail. There might be other major performance impact of Online Index Rebuild operation as well. Please consider below recommendations if you are using Online index operations or during SQL Server rebuild index online.

1. During ONLINE index rebuild and index creation, additional space is required in the data file to keep the second copy of the index. This is because SQL Server creates a snapshot of the index and once index rebuild or creation completes, second copy of this index will be removed by SQL Server.
2. Additional disk space is required for the temporary mapping index. This temporary index is used in online index operations that create, rebuild, or drop a clustered index.
3. Make sure the transaction log has been backed up and truncated before running index operations online, and that the log has sufficient space to store the projected index and user transactions.
4. Specify SORT_IN_TEMPDB option to ON for the index operation. This separates the index transactions from the concurrent user transactions. The index transactions will be stored in the tempdb transaction log, and the concurrent user transactions will be stored in the transaction log of the user database. Make sure to keep tempdb log and user database log files on separate drives to avoid any disk space issues.
5. Verify that the tempdb database and transaction log have sufficient disk space to handle the index operation. The tempdb transaction log cannot be truncated until the index operation is completed.
6. Do not run the online index operation in an explicit transaction. The log will not be truncated until the explicit transaction ends.

Performance Considerations

If we think about performance impact of Online Index Rebuild operation on SQL Server then it will put more burden on your database server than offline index operations. Because both the source and target structures are maintained during the online index operation.

ONLINE Index operations will be slower than equivalent offline index operations because insert, update, and delete transactions is increased, potentially up to double. This could cause a decrease in performance and greater resource usage, especially CPU time, during the index operation. Online index operations are enterprise features and are fully logged operations.

It is recommended to use legacy way of index rebuild or index operations if your system allows a maintenance window. Remember users will be restricted to access data during the offline index operation, but the operation finishes faster and uses fewer resources.

If you have a system that runs 24×7 then ONLINE index rebuild or creation will be a better choice but make sure to consider all points described in this article before choosing online index operations. You need to think from disk space and performance both prospect and design your system that can handle the load and sustain during peak hours.

Related Articles

• SQL Server Interview Questions & Answers on Indexes
• Understanding Different types of Indexes in SQL Server

Here, I have described Disk and Performance Impact of Online Index Rebuild operation on SQL Server. I hope you like this article. Please follow our Facebook page and Twitter handle to get latest updates.

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Related Articles:

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Types of Joins

 There are four types of Joins and each type is having separate ways to retrieve data.

• Inner Join
• Right Join
• Left Join
• Full Join

We will use two tables Employees and Leavesdetails to explain you each type of Joins with example. The details of both tables are given below.

Table Employees:

Table LeavesDetails:

 We will apply all types of Joins between these two tables to show you how they work. Let’s start with Inner Join. 

Inner Join 

Inner join will show data that is matched between both joined tables. This is default join where result is based upon where clause and matched value from all rows fetch data. The visual representation of inner join will look like below image. You can see the coloured area that is common between both tables and that will be output of INNER JOIN.

As per above image, both tables Employees and Leavesdetails have been joined together to get output details for rows that are matched to each other.

SELECT *
FROM EMPLOYEES
INNER JOIN [dbo].[LeavesDetails]
ON [LeaveDetails].[Employeeid]=[Employees].[Employeeid]

Right Join

When we use Right Join keyword, it will return all rows from table 2 that is placed right side of RIGHT JOIN keyword and matched rows from table 1 that is mentioned just left to the RIGHT JOIN keyword in SQL statement. In right join, if rows do not match with table 1 it will return null value. Sometimes, we call it as Right Outer Join as well. The visual diagram of Right Join is given below.

Example

We can see Employees table is mentioned as table 2 and placed just right after keyword RIGHT JOIN and Leavesdetails table has been mentioned as table 1 that is just left to the keyword RIGHT JOIN.

SELECT * FROM Leavesdetails
RIGHT JOIN Employees
ON [Employees].[Employeeid]=[Leavesdetails].[Employeeid]

You can see all values have been displayed from table Employees  along with corresponding details from table 2 Leavesdetails whereas there is one null value row from table Leavesdetails because there is no matched entry for this row from Employees table.

Left Join

When we use LEFT JOIN keyword, it will return all rows from table 1 that is placed just before or left side to the LEFT JOIN keyword and matched rows from table 2 that is mentioned just right side to the LEFT JOIN keyword in SQL statement. In left join, if rows do not match with table 2 it will return null value. Left Join is also known as left outer join. You can see the visual representation of Left Join in below image.

Example

you can see, now Employee table is mentioned left side of LEFT JOIN keyword and Leavesdetails table is mentioned in right side of this keyword so Employee table will work as table 1 and Leavesdetails will work as table 2.

SELECT *
FROM Employees
LEFT JOIN Leavesdetails
ON [Leavesdetails].[Employeeid]=[Employees].[Employeeid]

We can see all records from Employees table along with its corresponding details from table 2 Leavesdetails whereas one null values from table2 that is Leavesdetails because it’s matching with the data presented in table 1 Employees table. As highlighted record does not exist in table 2 it is showing null value.

Full Join

When we use FULL JOIN, it fetches results from both tables when there is a match in either in left or right table. We can also say it is kind of combination of left and right join.

Example

As visual representation shows, it will show all records from Employees table and Leavesdetails table. You can see in below result set Employee Manvendra has not any leaves detail and same way Employee ID 108 has not any record in Employees table but both rows are showing their values.

SELECT *
FROM EMPLOYEES
FULL JOIN [dbo].[Leavesdetails] on [Leavesdetails].[Employeeid]=[Employees].[Employeeid]

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UNION

The UNION operator allows us to combine the results of two or more SELECT statements into a single result set and removes duplicate rows from that result set. Basically, it is performing a DISTINCT operation across all columns in the result set. The UNION operator is different from using joins that combine columns from two tables.

The following are basic rules for combining the result sets of two queries by using UNION:

• The number and the order of the columns must be the same in all queries.
• The data types must be compatible.
• Corresponding result set columns in the individual statements that are being combined with UNION must occur in the same order, because UNION compares the columns one-to-one in the order given in the individual queries.
• The column names in the result from UNION are taken from the first individual query in the UNION statement.

Below example shows how can you use UNION to combine multiple outputs into one result set.

SELECT * FROM Table1
UNION
SELECT * FROM Table2
UNION
SELECT * FROM Table3

If tables would not have same structure or same data types, you will get below error while using UNION:

UNION ALL

UNION ALL operator also works like UNION operator that is used to combine multiple result sets into one result set but duplicate rows will not be removed from the result set using UNION ALL unlike the result set of UNION operator that gives distinct rows.

SELECT * FROM Table1
UNION ALL
SELECT * FROM Table2
UNION ALL
SELECT * FROM Table3

Difference Between UNION and UNION ALL ( UNION vs UNION ALL )

Please find important points if we compare the difference between UNION vs UNION ALL result sets and their uses.

• The UNION operator removes duplicate rows from the result set and gives us distinct rows whereas UNION ALL operator does not remove duplicate rows and give all outputs in the result set.
• UNION ALL operator works faster than UNION operator because it does not remove duplicate rows. UNION operator performs distinct sort to remove duplicate rows so its performance is little slower than UNION ALL.
• Operator UNION ALL works with all data type columns whereas UNION operator does not work with a column that has a TEXT data type and it will throw error during execution.

Guidelines to use UNION  and UNION ALL

I have discussed difference between UNION and UNION ALL in above section. Here i will explain below guidelines you should consider while using UNION and UNION ALL operators with other T-SQL statements. Below rules are also apply to EXCEPT and INTERSECT operator:

• The first query can contain an INTO clause that creates a table to hold the final result set. Only the first query can use an INTO clause. If the INTO clause appears anywhere else, SQL Server displays an error message.
• ORDER BY is allowed only at the end of the statement. It cannot be used within the individual queries that make up the statement.
• GROUP BY and HAVING clauses can be used only within individual queries; they cannot be used to affect the final result set.
• UNION, EXCEPT and INTERSECT can be used within an INSERT statement.
• The FOR BROWSE clause cannot be used in statements that involve the UNION, EXCEPT and INTERSECT operators.

Related Articles:

• How to Protect Stored Procedure Code?
• Create a Logon Trigger to Restrict sysadmin logins to Connect to SQL Server during a given time Interval
• How to get Total Row Count of all tables of a database

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Let’s check the row counts of tables using script that are using sys.partitions system catalog view and compare the output of a table with the output of SELECT COUNT (*) .

Get Row Counts of All Tables using sys.partitions or DMV sys.dm_db_partition_stats

System catalog view sys.partitions contains a row for each partition of all the tables and most types of indexes in the database. All tables and indexes in SQL Server contain at least one partition, whether they are explicitly partitioned. Run below script to get the row count of all tables in a database. If you want to find row counts using DMV sys.dm_db_partition_stats, i would suggest you to visit our attached article how to find row counts of all tables in a database.

--Run below script to get the row counts of all tables in a database.
SELECT      SCHEMA_NAME(O.schema_id) + '.' +
        O.Name As [Schema.TableName], SUM(P.rows) AS 'Total_RowCount'
FROM        sys.objects O
INNER JOIN sys.partitions P ON O.object_id = P.object_id
WHERE     O.type = 'U'
GROUP BY    O.schema_id, O.Name

You can see row count of all tables in below screenshot.

Now we will check row count of a table using SELECT COUNT(*) command. I ran below command and you can see that row count is not same here. Row count came using sys.partitions system catalog view has more value than the row count of SELECT COUNT (*).

As i said above “sys.partitions or DMV sys.dm_db_partition_stats contains a row for each partition of all the tables and most types of indexes in the database” so when you are fetching row counts of tables using sys.partitions system catalog view or DMV sys.dm_db_partition_stats, it will display the row counts after adding indexes row counts and table row counts. That is why value is showing more in sys.partitions or in sys.dm_db_partition_stats output.

Suppose you have a table with 5000 rows in it and you’ve defined 5 indexes on it, the above query would show 5*5000=25000 rows for that table. So, it isn’t just that some rows are inconsistence, it is that some rows are multiplied by the number of indexes they have.

If we need correct row count using the system cataog view sys.partitions then we need to put a condition in WHERE clause for index_id column. We can also get total row count of all the heap tables or for all the clustered index tables as well by changing the value of index_id mentioned in WHERE clause. Index_id value indicates the ID of the index within the object to which this table belongs.

• 0 = heap
• 1 = clustered index
• 2 or greater = nonclustered index

We can pass index_id value in above script to get the total row count of all tables whether it is heap or clustered index table. If you need total row count of all the tables present in a database, you should put index_id<2 condition in WHERE clause. Run below scripts to get the row count of all heap & clustered index tables.

--Run below script to get the row counts of all tables in a database.
--Change the value of index_id to 0 or 1 to get total row count to heap or cluster index tables.
SELECT      SCHEMA_NAME(O.schema_id) + '.' +
        O.Name As [Schema.TableName], SUM(P.rows) AS 'Total_RowCount'
FROM        sys.objects O
INNER JOIN sys.partitions P ON O.object_id = P.object_id
WHERE     O.type = 'U'
		AND P.index_id<2  
GROUP BY    O.schema_id, O.Name

Now you can run above script and compare the output with the SELECT COUNT(*) output. We can see row count for given table is showing same after adding idex_id condition in below screenshot.

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• Tables
• Heap tables only
• Clustered index tables only
• Tables having specific Schema

We can get total row counts of all tables using system catalog view sys.partitions or DMV sys.dm_db_partition_stats. Read attached article if you are getting wrong row counts using this DMV or catalog view. Let’s check the row counts using both ways in this tip.

Get Row Counts of Tables using sys.partitions

System catalog view sys.partitions contains a row for each partition of all the tables and most types of indexes in the database. Special index types such as Full-Text, Spatial, and XML are not included in this view. All tables and indexes in SQL Server contain at least one partition, whether or not they are explicitly partitioned. Run below script to get the row count of all tables in a database.

--Run below script to get the row counts of all tables in a database.
SELECT      SCHEMA_NAME(O.schema_id) + '.' +SELECT      SCHEMA_NAME(O.schema_id) + '.' + O.name As [Schema.TableName],  SUM(P.rows) AS [Total_RowCount] 
FROM        sys.objects O
INNER JOIN sys.partitions P ON O.object_id = P.object_id
WHERE     O.type = 'U' AND P.index_id<2  
GROUP BY    O.schema_id, O.name
ORDER BY [Total_RowCount] desc

You can see row count of all tables in below screenshot.

We can get total row count of all the heap tables or for all the clustered index tables as well by changing the value of index_id mentioned in WHERE clause. Index_id value indicates the ID of the index within the object/table. If index_id value is 0 that means that table doesn’t have any cluster index and a Heap table.

• 0 = heap
• 1 = clustered index
• 2 or greater = nonclustered index

We can pass index_id value in above script to get the total row count of all tables whether it is heap or clustered index table. Run below scripts to get the row count of all heap tables.

--Run below script to get the row counts of all Heap (tables without cluster index) in a database.
--Change the value of index_id from 0 to 1 to get total row count to cluster index tables.
SELECT      SCHEMA_NAME(O.schema_id) + '.' +
        O.name As [Schema.TableName], SUM(P.rows) AS [Total_RowCount]
FROM        sys.objects O
INNER JOIN sys.partitions P ON O.object_id = P.object_id
WHERE     O.type = 'U'
		AND P.index_id=0  --Change this value according to your need
GROUP BY    O.schema_id, O.name
ORDER BY [Total_RowCount] desc

You can see there are only two tables that have no cluster index in above screenshot. We can also get the row count of all tables having a specific schema by adding a condition in WHERE clause.

--Run below script to get the row count of all tables having dbo Schema in a database.
SELECT      SCHEMA_NAME(O.schema_id) + '.' +
        O.name As [Schema.TableName], SUM(P.rows) AS [Total_RowCount]
FROM        sys.objects O
INNER JOIN sys.partitions P ON O.object_id = P.object_id
WHERE     O.type = 'U'
		AND P.index_id<2  
		AND SCHEMA_NAME(O.schema_id) ='dbo'--Change dbo with your schema name for which you need row counts
GROUP BY    O.schema_id, O.name
ORDER BY [Total_RowCount] desc

You can see the output in below image. You can make changes as per your need.

Get Row Count of All Tables using DMV sys.dm_db_partition_stats

DMV sys.dm_db_partition_stats returns page and row-count information for every partition in the current database. We will leverage this DMV to get row count details of all tables. Run below script to get the row count of all tables using this DMV.

--Run below script to get the row count of all tables in a database.
SELECT QUOTENAME(SCHEMA_NAME(O.schema_id)) + '.' + QUOTENAME(O.name) AS [Schema.TableName]
      , SUM(p_dmv.row_count) AS [Total_RowCount]
FROM sys.objects AS O
      INNER JOIN sys.dm_db_partition_stats AS p_dmv
            ON O.object_id = p_dmv.object_id
WHERE  O.type = 'U'
        AND p_dmv.index_id < 2
GROUP BY
      O.schema_id
      , O.name
ORDER BY [Schema.TableName]
GO 

We can see the output of above script in below image.

We can pass index_id value in above script to get the total row count of all tables whether it is heap or clustered index table. Run below scripts to get the row count of all heap & clustered index tables.

--Run below script to get the row counts of all Heap (tables without cluster index) in a database.
--Change the value of index_id from 0 to 1 to get total row count to cluster index tables.
--Change the schema name if you want the row count of tables that are having specific schema.
SELECT QUOTENAME(SCHEMA_NAME(O.schema_id)) + '.' + QUOTENAME(O.name) AS [Schema.TableName]
      , SUM(p_dmv.row_count) AS [Total_RowCount]
FROM sys.objects AS O
      INNER JOIN sys.dm_db_partition_stats AS p_dmv
            ON O.object_id = p_dmv.object_id
WHERE  O.type = 'U'
        AND p_dmv.index_id < 2
	AND SCHEMA_NAME(O.schema_id) = 'dbo'--Change the name of your Schema to get row count of all tables having this schema.
GROUP BY
      O.schema_id
      , O.name
ORDER BY [Schema.TableName]
GO 

And here is the output:

I hope you like this article. You can comment about your questions in comment section. Please follow us on our facebook page and on Twitter handle to get latest updates.

Related Articles:

• Why rou count showing incorrect value in sys.partitions?
• Understanding Different Types of SQL JOINs with Examples
• Create a Logon Trigger to Restrict sysadmin logins to Connect to SQL Server during a given time Interval
• How to Protect Stored Procedure Code/Script?

The post How to Get Row Count of All Tables of a Database appeared first on Techyaz.com.

Logon trigger Overview

Logon Triggers fire in response to a LOGON event. It fires after the authentication phase of logging in finishes, but before the user session is actually established. Logon Triggers are very useful in tracking and restricting login events.

Sometimes few applications require sysadmin privilege to run and if you downgrade this access, application stops working. So, we cannot restrict sysadmin logins of such applications. There is always a scope of security breach if another login has sysadmin access except DBAs on SQL Server Instance.

To fix this issue, I have created a logon trigger that will restrict access of such application logins who are sysadmin on your SQL Server Instance.  We can restrict them to access SQL Server directly through SSMS or any other medium. You need to pass that medium into code just like I have passed Management studio.

Logon Trigger T-SQL Code

Below is the Logon Trigger T-SQL code which will be used to restrict any login for given time frame.

SET ANSI_NULLS ON
GO
SET QUOTED_IDENTIFIER ON
GO

CREATE trigger [logon_rest]
on all server for logon
as begin
declare @Program varchar(128)
declare @systemname varchar(128)
select @Program =PROGRAM_NAME,@systemname=HOST_NAME from sys.dm_exec_sessions as A
where a.session_id=@@SPID
if ORIGINAL_LOGIN() in('sa') /**Login For Which Access Need to restricted **/
and @Program like'%Management%studio' /** Program via access restricted **/
and
(GETDATE()>(dateadd(day, datediff(day, 0, getdate()), 0) + '18:00') /**Last time till access allowed **/
or
GETDATE()<(dateadd(day, datediff(day, 0, getdate()), 0) + '09:00')) /**Start time from access allowed **/
begin
Raiserror ('This is out of office hour',1,1)
rollback;
end
end;
GO
SET ANSI_NULLS OFF
GO
SET QUOTED_IDENTIFIER OFF
GO
ENABLE TRIGGER [logon_rest] ON ALL SERVER
GO

Testing

For the testing purpose, I have taken sa account as a potential application login. You can use your identified login which are running with sysadmin rights. Even we can restrict such logins to connect to SQL Server during given time frame.

Here we have disabled sa server level login to connect through SSMS Before 9:00 AM and Post 6:00 PM. That means server login sa cannot connect to SQL Server Instance between given time slot. You can alter the time slot as per your convenience.

Just for example we have tried to login on SQL server through SSMS between given time frame and here you can see the output. I am not able to connect to SQL Server anymore. You can see this in below screenshot. But at the same time you can login to the same SQL Server Instance using other sysadmin or normal login accounts which is available in sys.syslogins.

Even we can track the failed login attempt made on this SQL Server Instance once you can make a database connection using another login. You can check the SQL Server error logs or you can just run sp_readerrorlog stored procedure to display errors. You can see our test login attempt is showing in below screenshot on the server.

Read more about SQL Server Login Issue related Articles:

• How to fix Error 15173: Revoke the permissions before dropping the login.
• Fix error 15138 & Error 3729: DROP login failed
• How to fix error 15434: Could not drop login as the user is currently logged in
• Fixing error 15170: Login owns one or more SQL Agent Jobs

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We can use “WITH ENCRYPTION” option to protect our T-SQL code. Have a look at below SQL code that i have been used to protect my stored procedure.

CREATE PROCEDURE dbo.Manvendra
WITH ENCRYPTION
AS
BEGIN
SELECT 'SQL statements'
END

Now when you will try to run sp_helptext to see the code, below error will appear.

“The text for object ‘Manvendra’ is encrypted”.

Read Articles:

• How to Disable Autocommit in SQL Server?
• Create a Logon Trigger to Restrict sysadmin logins to Connect to SQL Server during a given time Interval
• How to Move a Table to another filegroup?
• New T-SQL Functions Introduced in SQL Server 2017

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Enable or Disable Autocommit using T-SQL

You can turn off auto commit by setting implicit_transactions ON. Run below T-SQL command to turn off autocommit in SQL Server.

SET IMPLICIT_TRANSACTIONS ON

When the setting is ON, it returns to implicit transaction mode. In implicit transaction mode, every change you make starts a transactions which you have to commit manually. When you need to enable it just run above command with OFF clause. Run below command to enable auto commit.

SET IMPLICIT_TRANSACTIONS OFF

autocommit is the default for Sql Server 2000 onwards.

Enable or Disable Autocommit using GUI

You can also turn off autocommit using SQL Server Management Studio by following below steps.

1. Connect to SQL Server Instance in SQL Server Management Studio.
2. From the Menu bar, click on Tools and then choose Options
3. Select Query Execution then SQL Server followed by ANSI
4. Make sure to click on check box SET IMPLICIT_TRANSACTIONS
5. Click on OK

Now, open a new Query window and start executing the scripts. If you want to turn it on the follow same steps as given above and uncheck the SET IMPLICIT_TRANSACTIONS option that are mentioned in step no 4.

Related Articles:

• How to get Total Row Count of all tables of a database?
• Understanding Page Split in SQL Server
• What should be the Best Value for Fill Factor?
• Top 21 New Features in SQL Server 2017 that is missing from SQL Server on Linux
• Read Why We should always Turn Off Database AutoShrink Database Property

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SELECT * FROM fn_trace_getinfo(default);
GO

You will get below output:

You can find out the no of traces through trace ID column/count. Now suppose you have to stop them then run below script:

--Replace TraceID with your TraceID number that you want to stop.
DECLARE @TraceID int
SET @TraceID = 2
EXEC sp_trace_setstatus @TraceID, 0
EXEC sp_trace_setstatus @TraceID, 2

Replace the trace id value with one which has to be stopped.

Related Article:

• What should be Best value for Fill Factor in SQL Server?
• Why Should You Always Turn Off Database Auto Shrink Property?
• Understanding SQL Server Database Autogrowth Property

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1. Identify the Large tables that we will be moving to another filegroup placed on drive E.
2. Create new filegroup on disk E and if you have already a filegroup in this drive you can use that one.
3. Add a data file to this newly created filegroup.
4. Drop the clustered index from the table that has been identified for the movement and recreate it to the another filegroup.
5. Create cluster index on the same table.

Move a table to Another Filegroup

We can move table from one filegroup to another filegroup through dropping and recreating the clustered indexes. Below T-SQL codes that will move your complete table from filegroup1 to filegroup2. Run below ALTER TABLE statement to move a table named TAB1 that has a cluster index named PK_TAB1 to another filegroup TEST_DATA_2.

ALTER TABLE TAB1 DROP CONSTRAINT PK_TAB1 WITH (MOVE TO TEST_DATA_2)
GO
ALTER TABLE TAB1 ADD CONSTRAINT PK_TAB1 PRIMARY KEY(TAB1_ID)
GO

where TAB1 is table name PK_TAB1 is clustered index key and TEST_DATA_2 is target filegroup. It’s not necessary to create the another filegroup in to separate disk. This method will be useful if you want to move a table from one filegroup to another filegroup irrespective of the filegroup drives.

If your table doesn’t have a clustering index by any reason, you can still move table by creating a clustering index and then follow the same process to move it.

Related Articles:

• Understanding SQL Server Indexes and difference between Clustered and Nonclustered Indexes
• Rebuild Index vs Reorganize Index Operations
• Understanding Fill Factor and its value
• Relation between Page Split and Fill Factor

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