MySQL:

IFNULL

Syntax:
IFNULL(expr1,expr2)

If expr1 is not NULL, IFNULL() returns expr1; otherwise it returns
expr2.

mysql> SELECT IFNULL(1,0);
-> 1
mysql> SELECT IFNULL(NULL,10);
-> 10
mysql> SELECT IFNULL(1/0,10);
-> 10
mysql> SELECT IFNULL(1/0,'yes');
-> 'yes'

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