statistics

An important query is suddenly slow. Is it because statistics are out of date? This is tricky to figure out, and updating statistics right away can make troubleshooting even harder. Learn how to use query execution plans to get to the heart of the question and find out if stats are really your problem, or if it’s something else. In this 35 minute episode: 00:39 SQL Server 2017 Announced 01:10 New video from Microsoft’s Joe Sack demonstrating Adaptive Query Processing 03:05 This week’s question: Are bad stats making my query slow?

Short answer: the SQL Server optimizer will know that the table was truncated, but statistics might not update when you expect.

For the long answer, let’s walk through an example using the WideWorldImporters sample database.

Whether I’m working as a DBA, a consultant, a teacher, or just answering questions in my inbox, I always end up needing a script to inspect statistics one way or another.

Here are some freshly written scripts for a classic DBA question: what’s going on in my stats?

Should you look at automatically created statistics on your tables in SQL Server to help you design better indexes? Learn why in this 20 minute video, or subscribe to the Dear SQL DBA podcast. No time to watch? Scroll on down, everything is written in article form below the video. Here’s this week’s question: Dear SQL DBA, I’ve noticed that many indexes in my data warehouse aren’t used frequently.

Want to learn more about managing statistics updates in SQL Server? Watch my 27 minute presentation on managing statistics.

I’ve been asked a lot of questions about updating statistics in SQL Server over the years. And I’ve asked a lot of questions myself! Here’s a rundown of all the practical questions that I tend to get about how to maintain these in SQL Server.

What are statistics? How often should you update them? Do you need a trace flag to make this easier? What are duplicate statistics, and do you need to drop them?

Join me for a live Hangout on Monday, April 18 at 8:30 AM Pacific / 11:30 AM Eastern to up your maintenance game!

Update: improved/more recent version of queries for this are here.

It can be pretty difficult to manage statistics in data warehouses, or even OLTP databases that have very large tables.