10 SQL Stored Procedures Best Practices
If you're working with SQL stored procedures, there are a few best practices you should be aware of. In this article, we'll go over 10 of them.
Stored procedures are an essential part of any database-driven application. They can improve performance, enforce security, and maintain data integrity. But like any tool, they must be used correctly to be effective.
In this article, we will discuss 10 best practices for writing SQL stored procedures. By following these best practices, you can write more efficient and reliable stored procedures.
1. Use SET NOCOUNT ON
When a stored procedure is executed, SQL Server returns two result sets. The first result set is the count of the number of rows affected by the stored procedure. The second result set is the actual data that was requested.
If you don’t use SET NOCOUNT ON, your application will have to process both result sets, even though it only needs the second one. This can lead to performance issues, as well as problems with your application logic.
By using SET NOCOUNT ON, you tell SQL Server not to return the first result set, which means your application will only have to deal with the data it needs. This can lead to a significant performance boost, as well as simpler and more reliable application code.
2. Return error information from stored procedures
If a stored procedure encounters an error, the default behavior is for the procedure to terminate and return control to the caller. This might not be what you want, especially if you’re running the stored procedure from within another application. In this case, you might want the procedure to continue running so that the application can gracefully handle the error.
To do this, you need to use the RETURN statement to return error information from the stored procedure. The RETURN statement can take two parameters: an error code and a message. The error code is an integer value that indicates the severity of the error. The message is a string that contains a description of the error.
For example, say you have a stored procedure that inserts data into a table. If the insert fails, you might want the procedure to return an error code of 1 and a message of “Insert failed.” This would allow the calling application to know that an error occurred and take appropriate action.
Returning error information from stored procedures is a best practice because it allows you to gracefully handle errors in your applications. It also makes it easier to debug stored procedures because you can see exactly what went wrong.
3. Avoid unnecessary recompilations of stored procedures
When a stored procedure is recompiled, SQL Server has to go through the entire process of parsing, optimizing, and generating an execution plan for the procedure. This can be a time-consuming process, especially if the stored procedure is large and complex.
Recompilations can also cause performance problems because they can introduce query plan instability. Query plan instability occurs when the execution plan for a query changes from one execution to the next. This can happen for a number of reasons, but one of the most common is recompilation.
Query plan instability can cause all sorts of problems, including suboptimal performance, increased CPU usage, and even errors. So, it’s important to avoid unnecessary recompilations whenever possible.
There are a few things you can do to avoid recompilations. One is to use the WITH RECOMPILE option when creating stored procedures. This will tell SQL Server to always recompile the procedure before executing it.
another is to use parameterized queries. Parameterized queries are queries in which the values of the parameters are passed into the query at runtime. This prevents SQL Server from having to compile the query each time it’s executed, since the query plan can be reused.
Finally, you can use the sp_recompile system stored procedure to manually recompile a stored procedure. This should only be done if absolutely necessary, as it can cause performance problems if used excessively.
4. Use table variables instead of temporary tables
Table variables are stored in memory, so they are much faster than temporary tables, which are stored on disk. Also, table variables use fewer resources than temporary tables, so your SQL stored procedure will run more efficiently. Finally, table variables can be used in conjunction with other features that temporary tables cannot, such as indexes and constraints.
5. Use the schema prefix when referencing objects
When you prefix your objects with the schema name, it makes it explicit which schema the object belongs to. This is important because if you have multiple schemas in your database, there’s a chance that an object in one schema could have the same name as an object in another schema. By using the schema prefix, you can avoid any ambiguity and make sure that the stored procedure is always referencing the correct object.
It’s also a good idea to use the schema prefix when creating stored procedures, so that they are automatically created in the correct schema. This way, you won’t have to remember to specify the schema every time you run the stored procedure.
6. Keep transactions short and sweet
Long transactions can cause blocking, which can lead to performance issues. In addition, if a transaction is rolled back, any changes that were made during the transaction will be undone. For these reasons, it’s important to keep transactions as short as possible.
If you do need to run a long transaction, consider breaking it up into smaller ones. This way, if one part of the transaction fails, the other parts can still be completed.
7. Don’t use cursors
Cursors are often used to iterate through a result set one row at a time, and while this might seem like a harmless enough task, it can actually have a major impact on performance. Cursors place a significant amount of overhead on the database server, which can lead to slow stored procedure execution times and degraded overall performance.
Additionally, cursors can be difficult to code correctly, and they can introduce bugs and errors into your stored procedures. For these reasons, it’s best to avoid using cursors altogether and instead find alternative ways to achieve the same results.
8. Consider using a GUID as a primary key
GUIDs are globally unique, so there’s no risk of duplicate keys. They’re also random, so there’s no way to guess what the next key will be. This makes them more secure than traditional integer-based primary keys.
Additionally, GUIDs can be generated outside of the database, so they can be used as a primary key even if the database doesn’t support them. This is especially useful for distributed systems where each node may have its own database.
Finally, GUIDs are often used as foreign keys in other tables. This can make joins simpler and more efficient.
9. Use sp_executesql for dynamic SQL
When you use sp_executesql, SQL Server compiles the query and reuses the execution plan. This is in contrast to using EXEC, which doesn’t compile the query and creates a new execution plan each time, which can lead to performance issues.
Additionally, sp_executesql supports parameterization, which can help prevent SQL injection attacks. So not only is sp_executesql more efficient, it’s also more secure.
10. Always use fully qualified object names
When you use a stored procedure, the code is compiled and stored in the database. This means that when the stored procedure is executed, the database engine doesn’t need to go through the process of resolving object names.
If you don’t fully qualify your object names, the database engine will have to resolve them every time the stored procedure is executed, which can lead to performance issues. In addition, it can also lead to problems if the objects are renamed or moved to a different schema.
So, to avoid these potential problems, always use fully qualified object names in your SQL stored procedures.