Invalid Group By Function :: MySQL

Firstly, I've read through the posts with matching names, and I've tried integrating some of the solutions but I cant seem to get this SQL Query to work...

The problem seems to revolve around the COUNT function on line 8.

Here it is..


SELECT `purchase_orders`.`purchase_order_id`,`purchase_orders`.`sequence_id`,`purchase_orders`.`order_number`,`vendors`.`name`,`purchase_orders`.`date`,COUNT(`purchase_order_items`.`purchase_order_id`) `item_count`,`purchase_orders`.`total_value`,`purchase_orders`.`status`,`users`.`first`
FROM (`purchase_orders`, `vendors`, `purchase_order_items`,`users`) 
WHERE `purchase_orders`.`aid`='c4ca4238a0b923820dcc509a6f75849b'AND`purchase_orders`.`vendor_id`=`vendors`.`vid`AND`purchase_orders`.`created_by`=`users`.`uid`AND`purchase_order_items`.`purchase_order_id`=`purchase_orders`.`purchase_order_id` AND `purchase_orders`.`purchase_order_id` LIKE '%122%' 
OR `purchase_orders`.`aid`='c4ca4238a0b923820dcc509a6f75849b'AND`purchase_orders`.`vendor_id`=`vendors`.`vid`AND`purchase_orders`.`created_by`=`users`.`uid`AND`purchase_order_items`.`purchase_order_id`=`purchase_orders`.`purchase_order_id` AND `purchase_orders`.`sequence_id` LIKE '%122%' 
OR `purchase_orders`.`aid`='c4ca4238a0b923820dcc509a6f75849b'AND`purchase_orders`.`vendor_id`=`vendors`.`vid`AND`purchase_orders`.`created_by`=`users`.`uid`AND`purchase_order_items`.`purchase_order_id`=`purchase_orders`.`purchase_order_id` AND `purchase_orders`.`order_number` LIKE '%122%' 
OR `purchase_orders`.`aid`='c4ca4238a0b923820dcc509a6f75849b'AND`purchase_orders`.`vendor_id`=`vendors`.`vid`AND`purchase_orders`.`created_by`=`users`.`uid`AND`purchase_order_items`.`purchase_order_id`=`purchase_orders`.`purchase_order_id` AND `vendors`.`name` LIKE '%122%' 
OR `purchase_orders`.`aid`='c4ca4238a0b923820dcc509a6f75849b'AND`purchase_orders`.`vendor_id`=`vendors`.`vid`AND`purchase_orders`.`created_by`=`users`.`uid`AND`purchase_order_items`.`purchase_order_id`=`purchase_orders`.`purchase_order_id` AND `purchase_orders`.`date` LIKE '%122%' 
OR `purchase_orders`.`aid`='c4ca4238a0b923820dcc509a6f75849b'AND`purchase_orders`.`vendor_id`=`vendors`.`vid`AND`purchase_orders`.`created_by`=`users`.`uid`AND`purchase_order_items`.`purchase_order_id`=`purchase_orders`.`purchase_order_id` AND COUNT(`purchase_order_items`.`purchase_order_id`) LIKE '%122%'
OR `purchase_orders`.`aid`='c4ca4238a0b923820dcc509a6f75849b'AND`purchase_orders`.`vendor_id`=`vendors`.`vid`AND`purchase_orders`.`created_by`=`users`.`uid`AND`purchase_order_items`.`purchase_order_id`=`purchase_orders`.`purchase_order_id` AND `purchase_orders`.`total_value` LIKE '%122%' 
OR `purchase_orders`.`aid`='c4ca4238a0b923820dcc509a6f75849b'AND`purchase_orders`.`vendor_id`=`vendors`.`vid`AND`purchase_orders`.`created_by`=`users`.`uid`AND`purchase_order_items`.`purchase_order_id`=`purchase_orders`.`purchase_order_id` AND `purchase_orders`.`status` LIKE '%122%' 
OR `purchase_orders`.`aid`='c4ca4238a0b923820dcc509a6f75849b'AND`purchase_orders`.`vendor_id`=`vendors`.`vid`AND`purchase_orders`.`created_by`=`users`.`uid`AND`purchase_order_items`.`purchase_order_id`=`purchase_orders`.`purchase_order_id` AND `users`.`first` LIKE '%122%'  
GROUP BY `purchase_orders`.`purchase_order_id`
ORDER BY `purchase_orders`.`purchase_order_id` ASC 
LIMIT 0,1

Solution

When you use COUNT(xxx) in a SQL, you need to use it in the HAVING clause:

e.g.

HAVING COUNT(xxx) > yyyy

Also, generally you want to GROUP BY the fields that you don't use aggregate functions on. For example:

SELECT person_name
     , SUM(bonuses)
  FROM person x
     , person_bonus y
 WHERE x.person_id = y.person_id

GROUP BY person_name

As I add additional columns to that SELECT statement, I need to either use another aggregate function (COUNT, SUM, etc.) on them, or I need to GROUP BY them.

And again, anything you are using an aggregate function on can be used in your HAVING clause:

    SELECT person_name
         , SUM(bonuses)
      FROM person x
         , person_bonus y
     WHERE x.person_id = y.person_id
   GROUP BY person_name
     HAVING SUM(bonuses) > 50000  // I wish :)