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When to use an index or a temporary in MySQL?
If you use the SQL_SMALL_RESULT option, MySQL uses an in-memory temporary table, unless the query also contains elements (described later) that require on-disk storage. A quick scan shows that you suffer from #1. And this blog from 2009 says that “using filesort” means that the sort can’t be performed with an index.
How to create a temporary table in MySQL?
It should be noted that the temporary table that we will be creating here today differs from a true temporary table in MySQL, in that we are not adding the TEMPORARY keyword to the CREATE TABLE statement.
Is there a way to remove duplicates in MySQL?
MySQL offers a virtually endless variety of options for dealing with duplicated data. Most can be updated or removed using one statement. However, there are times when multiple commands must be issued to get the job done. Today’s blog will present a solution that employs a temporary table along with a SELECT DISTINCT query.
What does it mean to use filesort in MySQL?
And this blog from 2009 says that “using filesort” means that the sort can’t be performed with an index. Since you’re ordering by a computed field, that’s going to be true, too. So, that’s what’s “wrong”. Evaluation of UNION statements, with some exceptions described later.
Can a query be improved using MySQL?
MySQL Explain: Using index, using temporary, using filesort. Can this query be improved? I’m working on a event tracking system which uses a handful of lookup tables as well as the primary logging table.
When to use a temporary table in Excel?
Well, the doc gives the exact reasons when “Using temporary” will appear: If there is an ORDER BY clause and a different GROUP BY clause, or if the ORDER BY or GROUP BY contains columns from tables other than the first table in the join queue, a temporary table is created. DISTINCT combined with ORDER BY may require a temporary table.