Mysql: Using GROUP_CONCAT & FIND_IN_SET in where without having or subquery

Question

Hi I have a simple example query below that is not what I am using in reality as it is far too complex to explain here. Basically this query is being used in a search in a web application.

Due to the amount of data that this query could pull out I am trying to avoid the use of HAVING or subqueries as it drastically increases the amount of time it takes to retrieve the data.

I want to use FIND_IN_SET in the where clause but obviously GROUP_CONCAT can't be used in the where clause so I am trying to something simple like the below but I don't think the variable is set in the where and no results are returned.

SELECT 
   v.message, 
   @cat_values:= GROUP_CONCAT(c.category_value) as cat_values
FROM
  #Where the audit message is stored
  AUDIT_ITEMS AS V 
  #Link table containing primary key of AUDIT_ITEMS and AUDIT_CATEGORIES 
  LEFT JOIN AUDIT_ITEM_CATEGORIES AS ic 
    ON V.UUID = ic.ITEM_UUID 
  #Gets category uuid from link table above
  LEFT JOIN AUDIT_CATEGORIES AS c 
    ON ic.CATEGORY_UUID = c.UUID 
  #Gets the category label/type
  LEFT JOIN AUDIT_CATEGORY_TYPES AS ct 
    ON c.CATEGORY_TYPE_UUID = ct.UUID 
WHERE TRUE
#example filter used below
AND FIND_IN_SET("Errored", @cat_values) > 0
...etc...

I have tried:

AND FIND_IN_SET("Errored", (SELECT GROUP_CONCAT(c.category_value))) > 0 

But it does seem slow.

Also tried:

   HAVING FIND_IN_SET("Errored", GROUP_CONCAT(c.category_value)) > 0 

But there must be a way of efficiently filtering results based on the values in the group_concat?

Answer 1

You are looking for a conditional in the having clause:

having sum(c.category_value = 'Errored') > 0

You don't need group_concat() for this part of the logic.

It is unclear why you think that having would have a performance penalty. The performance hit is in the aggregation step -- which you need when you use group_concat() in the select .