Update Statistics SQL Server: Everything Dev Needs to Know

Greetings Dev! If you’re reading this, then chances are you’re looking for some tips and tricks on how to update statistics on SQL Server. Fear not, because in this article, we will discuss everything you need to know about updating statistics on SQL Server. So, sit back, relax, and let’s dive in!

What are Statistics in SQL Server?

Before we delve into updating statistics, let’s first understand what statistics are in SQL Server. Simply put, statistics are data that provide information about the distribution of data in a table or index. They help SQL Server’s query optimizer create efficient execution plans for queries.

By default, SQL Server updates statistics automatically when a certain percentage of data in the table changes (e.g. 20%). However, there are times when updating statistics manually can be beneficial. Let us explore when and how to proceed with an update.

Why Update Statistics Manually?

There are several reasons why you might want to update statistics manually. One of the most common is when you notice that the queries are running slower than usual. This can be a sign that the query optimizer is using outdated statistics, resulting in inefficient execution plans.

Another reason to update statistics manually is when you’re performing bulk data changes (e.g. inserting or deleting a large number of rows). In such cases, updating statistics manually can help the query optimizer generate more accurate execution plans.

How to Update Statistics in SQL Server

Updating Statistics on a Single Table

To update statistics on a single table, you can use the following command:

Command	Description
UPDATE STATISTICS table_name	Updates statistics for all columns in the specified table.
UPDATE STATISTICS table_name (column_name)	Updates statistics for the specified column in the specified table.

For example, to update statistics on the Customers table:

UPDATE STATISTICS Customers;

To update statistics for the LastName column in the Customers table:

UPDATE STATISTICS Customers (LastName);

Updating Statistics on Multiple Tables

Updating statistics on multiple tables can be a tedious task, especially if you have a large database with many tables. Luckily, SQL Server provides a way to update statistics on all tables in a database using the following command:

EXEC sp_updatestats;

This command updates statistics for all tables and indexes in the current database. This can take a while to complete, so be patient.

FAQ

When Should I Update Statistics Manually?

You should update statistics manually when you notice that queries are running slower than usual, or when you’re performing bulk data changes.

How Often Should I Update Statistics?

The frequency of updating statistics depends on the rate of data change in your database. If there are frequent changes in data, then you might want to consider updating statistics more often (e.g. weekly). On the other hand, if your data changes infrequently, then updating statistics every few months might be sufficient.

Can I Disable Automatic Statistics Updates?

Yes, you can disable automatic statistics updates if you want to update statistics manually. To do this, you can use the following command:

ALTER DATABASE database_name SET AUTO_UPDATE_STATISTICS OFF;

Remember to turn it back on after you’re done updating statistics:

ALTER DATABASE database_name SET AUTO_UPDATE_STATISTICS ON;

Will Updating Statistics Affect My Data?

No, updating statistics does not modify your data in any way. It only updates the information about the distribution of data in your tables and indexes.

What Happens if I Don’t Update Statistics?

If you don’t update statistics, then the query optimizer might use outdated statistics to generate execution plans for queries. This can result in inefficient execution plans and slower query performance.

Conclusion

Updating statistics on SQL Server is an important task that can improve the performance of your queries. Knowing when and how to update statistics can help you optimize your database and reduce query execution time. We hope this article has provided you with the information you need to update statistics on SQL Server. Happy updating, Dev!