在 MYSQL 中使用 NOT IN 和 GROUP CONCAT

Question

I'am using the " GROUP_CONCAT " function with the " NOT IN " statement in my mysql query. But for unknown reason, it doesn't return the correct values:

Here is my query not working:

select firstname, lastname
from t_user
where (status_Id NOT IN(Select GROUP_CONCAT(id) from t_status where code = 'ACT'
or code = 'WACT'))

Returns 46 rows

Here is my query working:

select firstname, lastname
from t_user
where (status_Id NOT IN(1,4))

Returns 397 rows

The results of the of the GROUP_CONCAT subquery

 (Select GROUP_CONCAT(id) from t_status where code = 'ACT' or code = 'WACT') = 1,4.

It seems that the query take only care of the first item return by the GROUP_CONCAT subquery.

So I don't understand what's going on and why I do not have the same results in both cases.

Thanks in advance Gael

Answer 1

in this case, you don't need to use GROUP_CONCAT function because it returns a string value. AND
1, 4 is very different from 1 and 4 .

select  firstname, lastname
from    t_user
where   status_Id NOT IN 
        ( Select id 
          from t_status 
          where code = 'ACT' or code = 'WACT'
        )

and a better way to right the query is by using LEFT JOIN ,

SELECT  a.firstname, a.lastname
FROM    t_user a
        LEFT JOIN t_status b
            ON a.t_status = b.id AND
                b.code IN ('ACT', 'WACT')
WHERE   b.id IS NULL

Answer 2

It is possible to exploit the list generated from GROUP_CONCAT as your question asks. Thus, in general, you can use the list from GROUP_CONCAT as follows:

According to the specification , you can simply use FIND_IN_SET instead of NOT IN to filter a field by subquery

select firstname, lastname
from t_user
where NOT FIND_IN_SET(status_Id, 
    (Select GROUP_CONCAT(id) from t_status where code = 'ACT' or code = 'WACT')
);