Question

I have a query that doesn’t work. I’ve fixed the problem by using a single IN statement (the library I’m using to construct my queries was causing this to happen) but I’m still curious why this happens.

The query is as follows:

SELECT * FROM (`table`) 
WHERE     `field` = 'false' 
      AND `something` LIKE '%string%' 
      AND `status_id` IN ('1') 
      OR `status_id` IN ('2') 
      OR `status_id` IN ('3') 

The query to me makes sense: Select everything from the table where field = false and something is like string and status id is in 1 or status id is in 2 or status id is in 3

When there are multiple IN statements the LIKE portion of the query is completely ignored.

Any ideas why mutliple IN statements would cause the LIKE to be ignored? I can’t work out why: re-arranging the query has no affect (moving the LIKE to the end vs. the start)

Answer 1

Precendence? Shouldn’t you use brackets to differentiate the AND and OR? status_id IN (‘x’) will if true cause the rest of the expression to be ignored.

SELECT * FROM (`table`) 
WHERE     `field` = 'false' 
      AND `something` LIKE '%string%' 
      AND (`status_id` IN ('1') 
            OR `status_id` IN ('2') 
            OR `status_id` IN ('3') 
      )

which is the same as

SELECT * FROM (`table`) 
WHERE     `field` = 'false' 
      AND `something` LIKE '%string%' 
      AND `status_id` IN ('1', '2', '3')

Try it for yourself by seeing what comes out with this.

SELECT * FROM (`table`) 
WHERE     `field` = 'false' 
      AND `something` LIKE '%string%' 
      AND `status_id` IN ('1') 
      OR 1=1    

Ask yourself what this query should return