When is SQL-CTE very slow when joined Stack Overflow?
The query is fast when running on a tblCharge with a few thousand rows. I have condensed the query into a single statement, but the same issue persists: Edit: More playing around,I just don’t understand this. This query is instant (2ms):
How long does it take to run a CTE query?
Here’s the query that performs badly (22 minutes on our hardware) : When running both CTE queries separately, it’s super fast (0 secs in SSMS, returns 122 rows and 13k rows), when running the full query, with INNER JOIN on sEmail, it’s super slow (22 minutes)
What should I do if my CTE is slow?
Test each CTE on its own from top to bottom to see if/where execution times or row counts explode. This is easy to do in SSMS by adding a Just before the main query that pulls the CTEs together and highlighting and running the script down to that point. Verify that the culprit is correctly written with proper predicates.
When is a CTE joined to a long table?
I was actually joining two CTEs together but I guess this would apply to all long running queries when a CTE is joined to a LONG table (especially outer joins). Thanks for contributing an answer to Stack Overflow!
Why is MY SQL Server query so slow?
After pushing the whole query to the linked server, there is no reason to have the WHERE and GROUP BY in the external query. You can collapse the query into one level. After the rewrite, and if it is still slow, check the execution plan in the remote server.
What’s the difference between a CTE and a query?
There is no difference between the first query and the second as far as how it is parsed, compiled and executed. The execution plans will be identical. The difference is in readability. When subqueries are complex, it can be easier to pull them out and put them into CTEs then combine them in a WITH statement.