Coalesce and Nullif example

COALESCE:

If expression is NOT NULL then put the left expression here hourly_wage, if NULL then put the right value eg: here zero '0'
 
NULLIF:

It compares the two expression is equal or not if equal put null if not equal then put left expression here hourly_wage

Script:

CREATE  TABLE #wages

(

    emp_id        tinyint   identity,

    hourly_wage   decimal   NULL,

    salary        decimal   NULL,

    );

GO

INSERT dbo.#wages (hourly_wage, salary)

   select  10.00, NULL

union

   select 20.00, NULL

union

   select NULL, 20000.00

union

   select NULL, NULL

SELECT CAST(COALESCE(hourly_wage,0 ) AS int) AS 'coalses Salary Example',

nullif(hourly_wage,salary)  'null Salary Example',* FROM dbo.#wages

drop table #wages