Inserting a Zero instead of NULL while performing LEFT OUTER JOIN in MYSQL

Question

Is there a way to insert a zero instead of NULL while performing LEFT OUTER JOIN on two tables?

Suppose I have a query like this:

SELECT * FROM
(SELECT uID from Class) T1
LEFT OUTER JOIN
(SELECT pID from University) T2
ON T1.uID = T2.pID
CASE WHEN T1.uID IS NULL
    THEN 0
ELSE T1.uID
END AS uID`

Correct me if I'm wrong

Answer 1

use ISNULL(field, 0) this will insert zero if the field is NULL

Answer 2

CASE WHEN a.fieldname IS NULL 
       THEN 0
       ELSE a.fieldname
END AS fieldname

Answer 3

something like:-

SELECT * FROM
(SELECT ifnull(uID,0) as uID from Class) T1
   LEFT OUTER JOIN
 (SELECT ifnull(pID,0) as pID from University) T2
   ON T1.uID = T2.pID