Can MySQL temporary variables be used in a WHERE clause?

Question

Can MySQL use temporary variables in a statement WHERE?

For example, in the following query:

SELECT `id`, @var := `id` * 2 FROM `user`

@var successfully set twice to id

However, if I try to filter the result set to include only the results where @var is less than 10:

SELECT `id`, @var := `id` * 2 FROM `user` WHERE @var < 10

then I get no results.

How to filter results based on @var value?

Answer 1

You need to assign an alias and check it in the sentence HAVING:

SELECT id, @var := id * 2 AS id_times_2
FROM user
HAVING id_times_2 < 10

: , , . :

SELECT id, id * 2 AS id_times_2
FROM user
HAVING id_times_2 < 10

Answer 2

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