Need to write MySQL case statement - mysql

Question

I need to write a MySQL statement, but not sure how to write it using case statements.
I would like to write something like this:
SELECT
*
FROM
table
WHERE:
IF sign_off_1 IS NOT NULL AND sign_off_1 IS NOT EQUAL TO 'Director'
sign_off_1_status MUST BE EQUAL TO Complete
IF sign_off_2 IS NOT NULL AND sign_off_2 IS NOT EQUAL TO 'Director'
sign_off_2_status MUST BE EQUAL TO Complete
IF sign_off_3 is IS NOT NULL AND sign_off_3 IS NOT EQUAL TO
'Director' sign_off_3_status MUST BE EQUAL TO Complete
Does anyone know the correct syntax to write this query?

Answer 1

It's not clear what you want to achieve. Does a row need to satisfy all three conditions, or just one of them? Either result can be achieved without using CASE expressions.
If the requirement is to use CASE expressions, and you need all three conditions to be true, you could do something like this:
SELECT t.id
FROM mytable t
WHERE CASE
WHEN t.sign_off_1 <> 'Director' AND t.sign_off_1_status = 'Complete'
THEN 1
ELSE 0
END
+ CASE
WHEN t.sign_off_2 <> 'Director' AND t.sign_off_2_status = 'Complete'
THEN 1
ELSE 0
END
+ CASE
WHEN t.sign_off_3 <> 'Director' AND t.sign_off_3_status = 'Complete'
THEN 1
ELSE 0
END
= 3
If you only need one of the conditions to be true, you could replace = 3 with > 0.
Note that an inequality comparison to a literal is sufficient to guarantee the column is not null. (If the column is NULL, the inequality comparison will return NULL, rather than TRUE.)
Again, the same result could be achieved without using CASE expressions.

Answer 2

You need to use OR and AND operator to simulate if condition in where clause. Try this.
SELECT *
FROM table
WHERE ( sign_off_1 <> 'Director'
AND sign_off_1_status = 'Complete' )
OR ( sign_off_2 <> 'Director'
AND sign_off_2_status = 'Complete' )
OR ( sign_off_3 <> 'Director'
AND sign_off_3_status = 'Complete' )
OR ( sign_off <> 'Director'
AND status <> 'Complete')
Update: am not completely sure about your comment. But this is what i understood.
WHERE (( sign_off_1 <> 'Director'
AND sign_off_1_status = 'Complete' )
OR ( sign_off_2 <> 'Director'
AND sign_off_2_status = 'Complete' )
OR ( sign_off_3 <> 'Director'
AND sign_off_3_status = 'Complete' ))
AND ( sign_off <> 'Director'
AND status <> 'Complete')