Optimizing OR Clauses

Daniel Hutmacher looks at different ways of optimizing queries with multiple conditionals and different parameters:

The SQL Server query optimizer can find interesting ways to tackle seemingly simple operations that can be hard to optimize. Consider the following query on a table with two indexes, one on (a), the other on (b):

SELECT a, b
FROM #data
WHERE a<=10 OR b<=10000;

The basic problem is that we would really want to use both indexes in a single query.

We get to see a few different versions of the query as well as the execution plans which result.

Related Posts

Iterative Solutions To The Closest Match Problem

Itzik Ben-Gan has a follow-up article looking at row-by-row solutions to the closest match problem: Last month, I covered a puzzle involving matching each row from one table with the closest match from another table. I got this puzzle from Karen Ly, a Jr. Fixed Income Analyst at RBC. I covered two main relational solutions that […]

Read More

Speeding Up The First Responder Power BI Interface

Kellyn Pot’vin-Gorman hits the Go Faster button: The gist of this kit is that it is a database repository as part of the sp_BlitzFirst to collect monitoring alerting and performance metric data. Once you’ve set this up, then you can use a Power BI desktop dashboard as an interface for all that data.Now this is an awesome […]

Read More

Categories

March 2016
MTWTFSS
« Feb Apr »
 123456
78910111213
14151617181920
21222324252627
28293031