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.

Read More:

• What is the Difference between UNION and UNION ALL T-SQL Operators?
• Understanding Different types of SQL JOINs with their Examples
• How to get Total Row Count of all tables of a database
• How to Disable AutoCommit in SQL Server?

The post New T-SQL Functions Introduced in SQL Server 2017 appeared first on Techyaz.com.

• What would be Disk and Performance Impact if we rebuild indexes using ONLINE option?

Resumable Online Index Rebuild

This feature allows us to pause index rebuild operation during its execution at any point and resume it later from the point it was paused. You can use this feature in case you get any higher priority tasks or your server is running out of disk space or facing any performance issue. In addition, this feature rebuilds indexes using only a small amount of log space.

This feature allows us to resume an index rebuild operation after an index rebuild failure, such as after a database failover or after running out of disk space. We can also pause an ongoing index rebuild operation and resume it later. Resumable Online Index Rebuild allows us to rebuild large indexes without using a lot of log space.

Read More

• SQL Server Interview Questions & Answers on Indexes
• What should be Best Value for fill factor in SQL Server?
• How to Avoid Page Split in SQL Server?

Points to Consider

Below are the points you must keep in mind if you are choosing resumable online index rebuild operation.

1. When an index operation is paused, both the original index and the the newly created one require disk space and need to be updated during DML operations.
2. Enables truncation of transaction logs during an index rebuild operation (this operation cannot be performed for a regular online index operation).
3. Resumable Online Index Rebuild feature can be used only with Online Index Rebuild operation. You cannot use it for offline index rebuild operation.
4. We cannot rebuild an index that is disabled.
5. We cannot use ALL option to rebuild existing indexes.
6. Resumable Index Rebuild operation cannot be used to rebuild an existing index that has either computed column or timestamp column as part of the index key.
7. We cannot use SORT_IN_TEMPDB=ON option if we choose to use resumable index rebuild option.

How to use Resumable Online Index Rebuild?

I have given multiple examples to demonstrate the different use cases of resumable online index rebuild operation in this section. If we want to use the resumable index rebuild functionality, we need to execute the online index rebuild with RESUMABLE keyword because Resumable index rebuild supports only during online index rebuild, so we must specify ONLINE = ON along with RESUMABLE = ON option. You cannot use this feature until you mention RESUMABLE = ON in your code because RESUMABLE=OFF is the default value. Run below command to rebuild index online as resumable option.

ALTER INDEX INDEX_Name on Table_Name
REBUILD WITH (ONLINE=ON, RESUMABLE=ON) ;

We can also specify MAXDOP settings during online index rebuild as resumable option to use parallelism. Execute an online index rebuild as resumable operation with MAXDOP=1 by running below command.

ALTER INDEX INDEX_Name on Table_Name 
REBUILD WITH (ONLINE=ON, MAXDOP=1, RESUMABLE=ON) ;

We can also control execution or processing time of resumable online index rebuild by specifying MAX_DURATION option. It specifies the number of minutes that the resumable online index operation will be executed, before being paused. Execute an online index rebuild as resumable operation with MAX_DURATION set to 30 minutes.

ALTER INDEX INDEX_Name on Table_Name 
REBUILD WITH (ONLINE=ON, RESUMABLE=ON, MAX_DURATION=30) ;

Next, we will discuss about pausing these index rebuild operations that are running as resumable option in next section.

Pause Online Index Rebuild running with Resumable Option

If you want to manually pause a running resumable online index rebuild then you just need to use PAUSE clause in above ALTER INDEX statements. Run below command to pause a resumable index rebuild operation.

ALTER INDEX INDEX_Name on Table_Name PAUSE ;

Now we will discuss about how to resume a paused online index rebuild operation in next section.

Resume an Online Index Rebuild running with Resumable Option

As I have mentioned above, you can pause online index rebuild due to any reason. Let’s say suppose you pause it because it is taking lot of time to complete and consuming lot of system resources then you can either resume it later when system has enough resource to run this operation or you can resume it specifying a new value for MAXDOP setting that will allow this operation to use parallelism to finish this task.

Suppose you want to resume an online index rebuild for an index rebuild that was executed as resumable operation specifying a new value for MAXDOP set to 8.

ALTER INDEX INDEX_Name on Table_Name 
RESUME WITH (MAXDOP=8) ;

If you want to resume an online index rebuild for an index rebuild that was executed as resumable operation with the same values then you can remove the MAXDOP options from above command and execute the simple command given below.

ALTER INDEX INDEX_Name on Table_Name RESUME;

You can also resume an online index rebuild operation for an index rebuild that was executed as resumable with different parameters like you can set MAXDOP to 2, set the execution time for the index being running as resumable to 60 minutes and in case of an index being blocked on the lock wait 10 minutes and after that kill all blockers. Run below command to rebuild your indexes with above criteria.

ALTER INDEX INDEX_Name on Table_Name
RESUME WITH (MAXDOP=2, MAX_DURATION= 60 MINUTES,
WAIT_AT_LOW_PRIORITY (MAX_DURATION=10, ABORT_AFTER_WAIT=BLOCKERS)) ;

You can test it in your lower life cycle with multiple options and keywords to get in depth knowledge about this feature.

Abort a Resumable Index Rebuild operation

We can also abort resumable index rebuild operation which is running or paused by executing below T-SQL statement.

ALTER INDEX INDEX_Name on Table_Name ABORT ;

Once you will run above command, your index rebuild operation will be aborted.

Monitor Resumable Index Rebuild Operation

Microsoft has given a system view sys.index_resumable_operations that monitors and checks the current execution status for resumable Index rebuild. You can also get the progress details in percentage of resumable index rebuild operation using this system view.

There is a column named state in this system view that will let us know the state of the resumable index rebuild operation whether it is paused or still running. You can query this system view to see all the resumable index rebuild operations that are currently paused or running.

Run below command to list all resumable index rebuild operations that are in the PAUSE state. State column value zero means online index rebuild is running and value 1 means they are paused. You can also check the percent completion of all resumable index rebuild operations from column PERCENT_COMPLETE from the output received by below command.

SELECT * FROM  sys.index_resumable_operations WHERE STATE = 1;

Related Articles

• Performing Online Index Rebuild Operation
• Understanding SQL Server Indexes and difference between Clustered and Nonclustered Indexes
• Difference between Index Rebuild and Index Reorganize Operation

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SQL Server 2017 New Features in Database Engine

Let’s discuss SQL Server 2017 features. Below is the list of SQL Server 2017 new features introduced in database engine services.

SQL Server on Linux

SQL Server is not only Windows based RDBMS anymore now you can run it on different flavor of Linux operating systems.  Now you can develop applications with SQL Server on Linux, Windows, Ubuntu, or Docker and deploy them as well on these platforms. SQL Server can now compete more directly with other RDBMS like Oracle which are more popular on Linux. We can say that SQL Server on Linux is one of the most popular SQL Server 2017 features. You can read below articles if you want to install SQL Server on Linux based operating systems.

• 21 Missing Features in SQL Server on Linux
• Install SQL Server 2017 on Redhat Linux – Offline Installation
• Install SQL Server 2017 on Redhat Linux – Online Installation
• How to install SQL Server on Ubuntu – Offline Installation
• How to install SQL Server on Ubuntu – Online Installation

Adaptive Query Processing

SQL Server 2017 introduce a new generation of query processing improvements that will adapt optimization strategies to your application workload’s runtime conditions. During optimization, the cardinality estimation process is responsible for estimating the number of rows processed at each step in an execution plan. When estimates are inaccurate, the query optimizer may make poor decisions regarding algorithm selection and order of operations. This is also one of the most awaited SQL 2017 new features.

Prior to SQL Server 2017, if we make poor assumptions due to bad cardinality estimates, we do not change our query plan execution strategy during execution. Read attached article Adaptive Query Processing to learn more about it.

Resumable Online Index Rebuild

Resumable Online Index Rebuild is another SQL 2017 feature. Now we can pause and resume online index rebuild operation. This feature will be very helpful. Resumable Online Index Rebuild allows you to resume an online index rebuild operation from where it stopped after a failure. For example, you might need to temporarily free up systems resources in order to execute a high priority task or complete the index rebuild in another maintenance window if the available maintenance windows is too short for a large table. Read attached articles to understand in depth information about this feature.

• How to Use Resumable Online Index Rebuild in SQL Server?
• Performing Online Index Operations

Automatic Database Tuning

Automatic tuning is a database feature that provides insight into potential query performance problems, recommend solutions, and automatically fix identified problems. Automatic tuning in SQL Server, notifies you whenever a potential performance issue is detected, and lets you apply corrective actions, or lets the Database Engine automatically fix performance problems.

Graph Database Capabilities

SQL Server offers graph database capabilities to model many-to-many relationships. The graph relationships are integrated into Transact-SQL and receive the benefits of using SQL Server as the foundational database management system.

A graph database is a collection of nodes (or vertices) and edges (or relationships). A node represents an entity (for example, a person or an organization) and an edge represents a relationship between the two nodes that it connects (for example, likes or friends). Both nodes and edges may have properties associated with them.

Cluster less Availability Groups

Now we can configure AOAG\Alwayson Availability group without windows cluster in SQL Server 2017. This feature is added because of another new feature that is to configure AOAG between windows and Linux based SQL Servers. Now you don’t need a windows cluster in place if you want to configure AOAG between windows and Linux based SQL Servers.

Cross-OS AOAG

Availability Groups can now work across Windows-Linux to enable cross-OS migrations and testing. Now we can configure AOAG between windows based SQL Server and Linux based SQL Server. That is why, Microsoft has also given an option for clusterless AOAG.

New Functions

There are few new T-SQL functions added to SQL Server 2017. Below is the list of those new functions. You can click on hyperlinks to get more about them. These functions are very useful for SQL developers.

• CONCAT_WS
• TRANSLATE
• TRIM
• STRING_AGG

New DMVs

There are many new DMVs have been introduced as SQL 2017 new features. Below is the list of such DMVs that have been introduced in SQL Server 2017. You can click on hyperlinks to get more about them.

• sys.dm_tran_version_store_space_usage – Introduced to track version store usage per database.
• sys.dm_db_stats_histogram (Transact-SQL) is added for examining statistics.
• sys.dm_exec_query_statistics_xml
• sys.dm_os_host_info is added to provide operating system information for both Windows and Linux.
• sys.dm_os_sys_info has three new columns added: socket_count, cores_per_socket, numa_node_count.
• A new column modified_extent_page_count, is introduced in sys.dm_db_file_space_usage to track differential changes in each database file of the database.

New DMFs

Below is the list of new DMFs introduced in SQL Server 2017. You can click on hyperlinks to get more about them. 

• This DMF sys.dm_db_log_info is introduced to expose the VLF information similar to DBCC LOGINFO to monitor, alert, and avert potential transaction log issues caused due to number of VLFs, VLF size or shrinkfile issues experienced by customers.
• Another DMF sys.dm_db_log_stats, is introduced to expose summary level attributes and information on transaction log files. This is very useful for monitoring the health of the transaction log.

Here, i have explained about SQL Server 2017 new features. I hope you like this article. Please follow us on our facebook page and on Twitter handle to get latest updates.

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