Know How to Improve Query Performance in SQL Server

The primary function of SQL database server is to store and retrieve the data which is requested by other software applications. SQL Server offer in different editions with respect to its features like Enterprise, Standard, Workgroup, Express. This database server is a computer program providing database service to other programs known as the client-server model. Hence, it is used for the execution of Structured Query Language.

It is quite often to suffer performance issues for SQL queries, as users want a fast response on the data retrieval process. This can be due to performance degradation of the improper maintenance of database or queries are written inefficiently.

In order to maintain the database properly, there are various techniques to improve query performance in SQL server. This blog focus on various tips and tricks which one can follow to improve query performance in SQL Server.

 

User Queries

 

“I have a table which contains approximately 10 million records. Is there some option to improve query performance in SQL server? My colleague suggested to partition the table into filegroups, as this will help to split the table into different smaller tables. Could someone suggest the best possible way to improve SQL query?”

“My database is loaded with bulks of data. One of the tables has 30 million rows and I need to print all of them at once. Could I split the query so that it accesses the table in iterations? So, please suggest some ways to improve query performance in SQL server which will help me to resolve this scenario!”

“I have been facing a poor performance while working with Microsoft SQL Server. These data, I have observed that it takes more time to retrieve the data. Could someone guide some solution to improve query performance in SQL server? Any suggestion would be appreciated, thanks in advance.”

 

Tips to Improve Query Performance in SQL Server

 

There are different ways to improve query performance in SQL Server such as re-writing the SQL query, proper management of statistics, creation and use of indexes, etc. Hence, it is important to optimize queries to improve SQL performance.

• Index the predicates in JOIN, WHERE, ORDER BY and GROUP BY clauses.
  Without proper indexes, SQL queries can cause table scans which can lower the performance. Hence, it is recommended that all predicate columns are indexed
• SQL server first search the user-defined stored procedure from the master .mdf and then from the current database. Hence, avoid using prefix with a user-defined stored procedure
• Explore the tables used in the SELECT statement, so that filters can be applied in the WHERE clause. When there are queries with sub-selects, try to apply filters in the inner statement of the sub-selects
• Only the columns which are selected will be read while using a column-oriented database management system. Hence, if fewer columns are included in the query, the less I/O will occur
• Remove the JOINS from the unnecessary tables which will help to reduce the database processing time. Thus, by removing columns it is observed that data is retrieved from the database
• In the SELECT statement, avoid writing *. For instance, mention the name of the column which is required
• If possible avoid using nchar and varchar, as both the data types take double memory as that of char and varchar
• Try to avoid NULL in a fixed-length field. If there is a requirement to use NULL, then use varchar field which takes less space for NULL
• Avoid HAVING clause, as this clause is required only if the user needs to filter the result of an aggregations
• Create clustered and non-clustered Indexes and keep clustered index small. Sometimes, it is also used in a non-clustered index
• It is a smart approach to create indexes columns which have integer values instead of characters. As integer values takes less space than character values
• Use WHERE clause to limit the size of the resultant tables which were created with joins
• Select the appropriate Data Type. For instance, if there is a need to store strings, then use varchar in place of text data type. Try to use text data type, when there is a need to store large data which is more than 8000 characters
• To improve query performance in SQL server, use TABLOCKX while inserting into the table and use TABLOCK while merging
• Try to use SET NOCOUNT ON and TRY- CATCH which will help to avoid the deadlock condition
  Also, try to use WITH(NOLOCK) while querying the data from any given table to improve query performance in SQL server
• If table variable is used in place of temp table, it makes a great difference to improve SQL performance. As the use of temp tables requires interaction with TempDb database which is a time-consuming task
• If UNION ALL is used in place of UNION, this improves the speed and thereby improves the SQL performance
• In case of complex and frequently used queries, use Stored Procedure for rapid data retrieval
• Multi-statement Table-Valued Functions (TVFs) are expensive compared to inline TVFs. Hence, avoid using Multi-statement TVFs

Also Read: Best Ways to Find Performance Issues in SQL Server Efficiently.

Conclusion

 

At times, most of the users face poor performance with SQL queries. By reading the various tips which are mentioned in this blog, one can practice it to improve query performance in SQL server. This blog clearly explains the solutions to improve SQL performance by giving few user queries also.