MySQL - help with IF... ELSE usage within query

I need to add an if/else stament inside a MySQL query but can't get it to work.

Below is an example with pseudo-code of what I want to accomplish.

SELECT *
FROM calendar
WHERE calendar.alert = 1

IF calendar.repeat = 0 THEN HAVING calendar.UTC_1 >开发者_如何学Go; UNIX_TIMESTAMP();

ELSE "get all records regardless of calendar.repeat value";

END IF;

Any suggestions to make this happen? I couldn't find the correct syntax for this MySQL IF ELSE.

Thanks for helping!

SELECT *
FROM calendar
WHERE calendar.alert = 1 
AND CASE 
WHEN `repeat` =0 THEN UTC_1 > UNIX_TIMESTAMP()
ELSE 1=1 END;

You can use IF-ELSE only inside the body of stored procedure/trigger. You can use IF(condition, value_if_condition_is_true, value_if_condition_is_false) in SELECT, but I prefer CASE(you can easily rewrite the query above to

 .... AND IF(`repeat` = 0, UTC_1>UNIX_TIMESTAMP(),1=1)

Not sure I got the syntax all right here, but I like the idea of somethign like this. In my opinion it is much easier to look at in the future and see the two groups you're grabbing with the following example. I'm not educated on efficiency of case vs union in MySQL but it seems to me like the case would be less efficient as well. Maybe someone can answer that for sure?

SELECT *
FROM calendar
WHERE 
    calendar.alert = 1
    AND calendar.repeat = 0
    AND calendar.UTC_1 > UNIX_TIMTESTAMP();
UNION
SELECT *
FROM calendar
WHERE
    calendar.alert = 1
    AND calendar.repeat != 0