Question : This query gets a list of posts created by people you follow. You can follow an unlimited number […]
Category: Database Optimization
multiple calls to procedure optimization
Question : I have multiple python scripts running statistical tests and saving the results in a MySQL database. I have […]
Why do we have Top N Sort in this example?
Question : In the example below the result of Index Spool is already sorted, why do we have Top N […]
Slow Performance caused by Correlated Sub-queries & Clustered Index Seek
Question : I’m running a query in which one of the tables (FIELDDATA) has nearly 400,000 records which is taking […]
Two-column index (pretty unequal columns) and database optimisation
Question : I’m thinking about creating an index on a table like this: primary | type | id 1 a […]
Optimize MySQL Query with multiple subqueries
Question : I have the following Query: SELECT p.id AS post_id, p.status, p.user_id AS post_user_id, ( SELECT pl.id FROM postlocks […]
How do I find the least optimised query?
Question : A library uses a relational database to store data about library books, their members and lending (books, which […]
Avoiding temporary tables while sorting by a column in a different table
Question : So I have this MySQL InnoDB query here: SELECT s.vid, s.body, s.timestamp, COUNT(v.id) AS votecnt FROM stories s […]
Why does SQL Server not perform constant (UNION ALL) branch elimination with OPTION(RECOMPILE) when selecting the result into a scalar variable?
Question : We use some ‘aggregate’ views to select from multiple tables using a discriminator (note: these views are not […]
SQL Server OR operator causing massive loop join
Question : The query below is very slow (running over a minute) and I have narrowed down the issue to […]