query-optimization Archives

MySQL, Programming

IT Nursery

JOIN queries vs multiple queries

Are JOIN queries faster than several queries? (You run your main query, and then you run many other SELECTs based on the results ...

May 27, 2022
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MySQL indexes – what are the best practices?

I’ve been using indexes on my MySQL databases for a while now but never properly learnt about them. Generally I put an index ...

May 24, 2022
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SQL: How to properly check if a record exists

While reading some SQL Tuning-related documentation, I found this: SELECT COUNT(*) : Counts the number of rows. Often is improperly used to verify ...

May 19, 2022
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Counting DISTINCT over multiple columns

Is there a better way of doing a query like this: SELECT COUNT(*) FROM (SELECT DISTINCT DocumentId, DocumentSessionId FROM DocumentOutputItems) AS internalQuery I ...

May 18, 2022
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