What are some common SQL performance tuning techniques?

Here are some common SQL performance tuning techniques:

Use appropriate data types: Choose the smallest data type that can accurately store the data. This will reduce the amount of space required to store the data and improve the performance of queries that involve those columns.
Create indexes: Indexes can help the database to quickly find the data that you need. Create indexes on the columns that are most frequently used in your queries.
Normalize your data: Normalization is a process of organizing data in a database to reduce redundancy and improve efficiency. Normalized databases are easier to query and maintain, and they can also improve performance.
Use efficient query patterns: Avoid using subqueries whenever possible. Instead, use joins to combine data from multiple tables.
Use appropriate WHERE clauses: Filter the data as early as possible in the query. This will reduce the amount of data that needs to be processed and improve performance.
Use limit and offset clauses: If you only need to return a subset of the data, use the LIMIT and OFFSET clauses to limit the number of rows that are returned. This can improve performance for large tables.
In addition to these general techniques, there are a number of specific SQL performance tuning techniques that can be used depending on the specific database and query. For example, you can use the EXPLAIN statement to analyze the execution plan of a query and identify areas where performance can be improved.

Here are some additional tips for SQL performance tuning:

Keep your database statistics up-to-date. This will help the database to choose the best execution plan for your queries.
Regularly defragment your database. This will improve the performance of queries that involve scanning the entire table.
Monitor your database performance and identify slow queries. Once you have identified slow queries, you can use the techniques above to tune them for better performance.