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等同:
CASE
WHEN (expression1 IS NOT NULL) THEN expression1
...
WHEN (expressionN IS NOT NULL) THEN expressionN
ELSE NULL
END
SET NOCOUNT ON;
GO
USE master;
IF EXISTS (SELECT name FROM sys.tables
WHERE name = 'wages')
DROP TABLE wages;
GO
CREATE TABLE wages
(
emp_id tinyint identity,
hourly_wage decimal NULL,
salary decimal NULL,
commission decimal NULL,
num_sales tinyint NULL
);
GO
INSERT wages VALUES(10.00, NULL, NULL, NULL);
INSERT wages VALUES(20.00, NULL, NULL, NULL);
INSERT wages VALUES(30.00, NULL, NULL, NULL);
INSERT wages VALUES(40.00, NULL, NULL, NULL);
INSERT wages VALUES(NULL, 10000.00, NULL, NULL);
INSERT wages VALUES(NULL, 20000.00, NULL, NULL);
INSERT wages VALUES(NULL, 30000.00, NULL, NULL);
INSERT wages VALUES(NULL, 40000.00, NULL, NULL);
INSERT wages VALUES(NULL, NULL, 15000, 3);
INSERT wages VALUES(NULL, NULL, 25000, 2);
INSERT wages VALUES(NULL, NULL, 20000, 6);
INSERT wages VALUES(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 wages;
GO
--返回其参数中的第一个非空表达式。
--例:
declare @i int,@j int,@n int,@k int
set @n=5
set @k=6
select COALESCE(@i,@j,@n,@k)
/*
-----------
5
(1 行受影响)
*/