Inserting Zero instead of NULL when executing LEFT OUTER JOIN in MYSQL

Question

Is there a way to insert null instead of NULL when doing a 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 am wrong

Answer 1

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

Answer 2

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

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