[RESOLVED] Problem with WHERE

[Paul_Ferrie]

Hi guys i am trying to pull records from a table but my query is not quite working.

SELECT *
FROM $table
WHERE recog = 'no'
AND category = '8'
OR category = '12'
ORDER BY id DESC
LIMIT 0 , 18

It's seems to ignore the check for 'recog'

Any idea what I am missing?
I am not a day to day php coder. I just know bits and pieces.

Any help apppreciatted

[bradgrafelman]

Why do you say it's "not quite working" ? Is it returning rows you didn't expect? If so, can you show us some of those rows? Is it not returning the rows you did expect? If so, can you show us some of those rows?

Paul Ferrie wrote:

I am not a day to day php coder. I just know bits and pieces.

That's quite alright, especially since what you posted has nothing to do with PHP! 😉

[Paul_Ferrie]

Hi 🙂

The problem is that it is returning data that dosen't match the recog='no'
It just seems to ignore this.
Attached is image of rows returned.

Thanks for taking the time to have a look 🙂

[bradgrafelman]

Try adding parenthesis to make the logic clear (to both you/us and MySQL 😉), e.g.:

SELECT * 
FROM $table 
WHERE
    recog = 'no' 
    AND (
        category = '8' 
        OR category = '12'
    )
ORDER BY id DESC 
LIMIT 0 , 18 

[Paul_Ferrie]

Thank you.
I would have never thought to try and put the second check in brackets

[bradgrafelman]

Just to explain further for clarification...

Your problem had to do with Operator Precedence. 'AND' has a higher precedence than 'OR', so all of the following are logically identical:

x AND y OR z
(x AND y) OR z
z OR x AND y
z OR (x AND y)

However, what you wanted was actually:

x AND (y OR z)

and in order to achieve that, you have to override the default operator precedence and force the desired grouping using parenthesis.