SQL Performance Tuning Tips for Quicker, Better Results

Anyone using the database always wants and expects a quick response to their queries and requests. This is one of the reasons why an organization requires a robust design for its database that focuses on giving optimal performance during data fetching and manipulation.

 

Although there isn’t a particular method to gauge database performance, both of these help the database administrator determine how well the database or an application connected to it is functioning. And if it is found lagging due to some reason, those reasons are found before selecting the appropriate method to perform SQL performance tuning and improve database speed.

 

Yes, there are multiple ways to improve SQL database performance, including the increased use of indexes and subqueries that introduce joins. In this article, we will discuss the top methods to gain better results and efficiency. Consider the following:

 

Let’s begin with some general tips, such as using EXISTS in place of IN, especially when you’re trying to verify the existence of information. When you type a SELECT query, try not to use *; instead, provide the exact names of the required columns.

 

You may already know about the use of the HAVING clause during MySQL SQL performance tuning. However, be careful to use it only if you want to filter the output of aggregate queries. Also, steer clear of sub-queries by using joins in their stead.

 

To further optimize your search results and database performance, place limits on the query with the help of the WHERE clause. Doing this will make the results tables created using joins smaller. On the other hand, if you’re in the process of using UNION in your query, use UNION ALL instead.

 

Every database expert recommends the use of indexes - both clustered and non-clustered. However, they suggest letting go of unused indexes as soon as possible and making the clustered index small because the fields present in one of those could also be used in a non-clustered index.

 

When creating a non-clustered index,  position highly selected columns on the leftmost side of the key. It is advisable to make indexes on columns containing numerical values rather than those with characters. This is because the former takes up a lower overhead in comparison with their alphabetical counterparts.

 

Tables are also important to consider when tuning SQL queries: for instance, users are advised to apply locks in their insertion (TABLOCKX) and merge (TABLOCK) queries. For statements that fetch data from the table using WITH, it is important to use WITH (NOLOCK).

 

Preventing deadlocks become simpler if you utilise SET NOCOUNT ON along with try-catch statements. Another way to improve performance during SQL performance tuning is by not using cursors because they slow down the database.

 

Certain tips help during table data manipulation as well. To begin with, incorporate table variables rather than temp tables because the latter need to interact with the temp DB database - and that takes a significant amount of time.

 

The positioning of names and variables makes a big difference as well. The schema the name should be followed by object names and try to apply the stored procedure for complicated statements as well as information that’s accessed and utilised more often.

 

Try to maintain as small transactions as you can because these are responsible for locking processing tables, which typically lead to deadlocks. Additionally, you need to pick suitable data types, such as using varchar instead of text when saving strings, and using text for storing bigger amounts of information (whose size exceeds 8000 characters).

 

Speaking of data types, try to skip the use of nchar and nvarchar wherever you can as these occupy twice the memory capacity required for char and varchar. Also, if your fields are of fixed lengths, do not use NULL unless absolutely necessary. When you do, use it with a data type that takes less space, such as varchar.