What is the use of COALESCE in SQL Server?

If all 3 attributes are null then?

"If all 3 attributes are null then?"
Then it will return as NULL . We can handle following way.

#1. So we need to handle in our server side code.

#2. SELECT ISNULL((CAST(COALESCE(hourly_wage, salary, commission) AS money)),0) AS 'Total Salary'
FROM wages;
It will return 0.00

coalesce function is used to replace the first not null value from an expression
check the below example-
if we have a table having name,mobileno,landline as columns
name mobileno landline
abc 9892133 null
def null 0223111
ghi null 0112233
jkl 998822 null
mno 998299 04488822
pqr null null
then the result of follwing query
select name,coalesce(mobileno,landline) as contact from tablename
would return the result
name contact
abc 9892133
def 0223111
ghi 0112233
jkl 998822
mno 998299 (first not null value)
pqr