Methods for Rewriting SQL Queries

Bert Wagner puts together a list of 12 techniques for tuning SQL queries:

6. DISTINCT with few unique values
Using the DISTINCT operator is not always the fastest way to return the unique values in a dataset. In particular, Paul White uses recursive CTEs to return distinct values on large datasets with relatively few unique values. This is a great example of solving a problem using a very creative solution.

Click through for the full list as well as a video demonstration.

Related Posts

Testing Inline Scalar UDF Performance

Erik Darling whips up a performance test covering scalar UDF changes in SQL Server 2019: This is a slightly different take on yesterday’s post, which is also a common problem I see in queries today. Someone wrote a function to figure out if a user is trusted, or has the right permissions, and sticks it […]

Read More

Making Non-SARGable Queries SARGable with an Index

Denis Gobo violates Betteridge’s Law of Headlines: This question came up the other day from a co-worker, he said he couldn’t change a query but was there a way of making the same query produce a better plan by doing something else perhaps (magic?) He said his query had a WHERE clause that looked like […]

Read More

Categories

May 2019
MTWTFSS
« Apr Jun »
 12345
6789101112
13141516171819
20212223242526
2728293031