Correct usage of If/else condition in MySQL based on a session variable

Question

If I set a session variable (eg. @tmp = 0), then a query can be run/ignored depending on whether a condition is met.

SET @create_table := IF(@tmp >= 1, 'CREATE TABLE table2 SELECT * FROM table1', 'no');

This is usable for a short query like the example above, but not so for more complex queries with multiple statements. Is it possible to do something like this?

IF(@tmp >= 1)
DO SOMETHING
ELSE
DO NOTHING

Do not confuse IF() function and IF statement. The function can be used as any other function (your 1st code) whereas the statement can be used in stored object only (procedure, function, trigger, etc.). — Akina
– Akina, Commented Nov 11, 2021 at 12:54

Dark Knight · Accepted Answer · 2021-11-11 12:54:05Z

1

The correct syntax is as follow.

IF condition1 THEN
   {...statements to execute when condition1 is TRUE...}

[ ELSEIF condition2 THEN
   {...statements to execute when condition1 is FALSE and condition2 is TRUE...} ]

[ ELSE
   {...statements to execute when both condition1 and condition2 are FALSE...} ]

END IF;

answered Nov 11, 2021 at 12:54

Dark Knight

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