MySQL - Why does it return NULL due to a MySQL function?

Question

MySQL

There is a request:

SELECT `password`,UPPER(md5(GROUP_CONCAT(CONCAT_WS(':',`pl_id`,`password`)))) FROM `admins` WHERE name = '%s' AND pl_id = '%d'

If nothing is found then NULL is returned, how to use IS NOT NULL in this situation?

Answer 1

If nothing is found, then the returned cursor will contain 0 entries, not NULL.
Although any operations with a NULL value return a NULL value.
PS: It's a bit unreasonable to store passwords in the database in plaintext. Any hack leads to the direct disclosure of passwords. It is much safer to store only md5 calculated along with the salt. Even the known value of the salt makes it difficult to directly access the data.

Answer 2

SELECT 
    CASE WHEN COUNT(`password`) = 0 THEN
      'There is no results'
    ELSE UPPER(md5(GROUP_CONCAT(CONCAT_WS(':',`pl_id`,`password`)))) END AS
  'str'
FROM portal.`channels` c
WHERE name = '%s' 
AND pl_id = '%d'