COALESCE 函数

SET NOCOUNT ON;
GO
USE tempdb;
IF OBJECT_ID('dbo.wages') IS NOT NULL
    DROP TABLE wages;
GO
CREATE TABLE dbo.wages
(
    emp_id        tinyint   identity,
    hourly_wage   decimal   NULL,
    salary        decimal   NULL,
    commission    decimal   NULL,
    num_sales     tinyint   NULL
);
GO
INSERT dbo.wages (hourly_wage, salary, commission, num_sales)
VALUES
    (10.00, NULL, NULL, NULL),
    (20.00, NULL, NULL, NULL),
    (30.00, NULL, NULL, NULL),
    (40.00, NULL, NULL, NULL),
    (NULL, 10000.00, NULL, NULL),
    (NULL, 20000.00, NULL, NULL),
    (NULL, 30000.00, NULL, NULL),
    (NULL, 40000.00, NULL, NULL),
    (NULL, NULL, 15000, 3),
    (NULL, NULL, 25000, 2),
    (NULL, NULL, 20000, 6),
    (NULL, NULL, 14000, 4);
GO
SET NOCOUNT OFF;
GO
SELECT CAST(COALESCE(hourly_wage * 40 * 52, salary,commission * num_sales) AS money) AS 'Total Salary' 
FROM dbo.wages
ORDER BY 'Total Salary';
GO
--COALESCE(Class, Color, ProductNumber) AS FirstNotNull 


select coalesce(hourly_wage, salary, commission, num_sales) as ds from dbo.wages
select coalesce(hourly_wage, salary, commission) as ds from dbo.wages
select * from dbo.wages
select coalesce(hourly_wage,num_sales) as ds from dbo.wages
select * from dbo.wages