The DB2 Coalesce function returns the value of the first non-NULL expression. The Coalesce function takes a comma separated list of arguments which are evaluated in the order in which they are specified and returns the first non-NULL value found.
Syntax : Coalesce(expr1, expr2, …., expr_n)
Example : Assume that Score1 and Score2 are columns in table Grades and that nulls are allowed in Score1 but not in Score2.
Select * From Grades
Where Coalesce(Score1,0) + Score2 > 100;
When this query is run, if the Score1 is null, it will be assumed as 0.
Suppose if the table Grade has 2 rows as follows:
Row 1 null 120
Row2 20 60
1st row will be returned ( Score1 will be assumed as 0.)