MySQL stored procedures use if subqueries to determine what to pay attention to

This article mainly introduces what MySQL stored procedures need to pay attention to by using if sub-query, which has a certain reference value. Interested friends can refer to it. I hope you will gain a lot after reading this article. Let the editor take you to know it.

MySQL stored procedure

Environment 5.6.14

Drop procedure if exists p

DELIMITER $$

CREATE PROCEDURE `p` ()

BEGIN

Start transaction

If (select 10 from dual where 1: 1 < 5) then

Select 'true'

Else

Select 'false'

End if

Commit

END $$

DELIMITER

Call p

Sometimes to save trouble, a subquery is used in if to return a value and then make a comparison.

Just like the above test process.

But when it is actually executed, the procedure returns true. Basically ignored the results of select, all entered the branch of true.

I think MySQL takes the judgment behind where as the content of comparison, and the above process seems to compare if ((1) 1).