mysql syntax for IFNULL with subquery - mysql

Question

I want to use subquery inside of IFNULL statement
SELECT t.col1
, IFNULL(t.col2, (SELECT an.col_11
FROM another_table an
WHERE an.col1 = t.col5)) as alias_name
, t.col3
FROM table t;
In IFNULL statement second expression should be subquery.
Please give me proper syntax
My actual query is
SELECT u.username, up.gender, d.name, desg.name,
IFNULL(up.creative_lead_id,
(SELECT au.username FROM auth_user au
WHERE au.id=up.creative_lead_id)) as creative_lead, up.image
FROM user_profile up, department d, designation, auth_user
WHERE up.department_id=d.id
AND up.designation_id = desg.id up.auth_uesr_id = u.id;
This query is giving syntax error because of IFNULL statement.

Answer 1

You can rewrite your query with join,Correlated query will execute for each row in your table and it might affect the performance
SELECT
t.col1,
IFNULL(t.col2, an.col_11) AS alias_name,
t.col3
FROM
`table` t
LEFT JOIN another_table an
ON an.col1 = t.col5

Answer 2

Don't use a subquery for this situation, try a query like that instead (use of jointure):
SELECT t.col1
,IFNULL(t.col2, an.col_11) AS alias_name
,t.col3
FROM your_table t
LEFT JOIN another_table an ON an.col1 = t.col5
In your full query, your using twice up.creative_lead_id for your IFNULL clause (once as first parameter and then in the subquery). That make no sense because if the first param is NULL, your subquery will return no result!
In order to show you the principe that will solve your problem, i just replaced the first param by a fictive one that i called up.creative_lead. This fictive column is the name of the creative lead stored in your table user_profile and if this value is null, i'm looking to the username of the user corresponding to creative_lead_id.
Here is the full query that'll solve your problem with the correction mentioned above:
SELECT u.username
,up.gender
,d.name
,desg.name
,IFNULL(up.creative_lead, cl.username) AS creative_lead
,up.image
FROM user_profile up
INNER JOIN department d ON d.id = up.department_id
INNER JOIN designation desg ON desg.id = up.designation_id
INNER JOIN auth_user u ON u.id = up.auth_user_id
INNER JOIN auth_user cl ON cl.id = up.creative_lead_id
Notice that i changed the syntax of your query, it's highly recommended to avoid the use of old syntax for jointures (use explicit JOIN clause instead).
Hope this will help you.