SQL 触发器语句

[weixin_44253967]

SQL 触发器语句
判断 当表更新 或者插入行的时候，判断 表中的刚插入或更新的A列的值，如果这个值大于0.2 就用B列的值去减去A列的值，然后反写到C列。 请问这种触发器如何编写

[weixin_44253967]

别沉啊别沉啊

[吉普赛的歌]

USE tempdb
GO
IF OBJECT_ID('t') IS NOT NULL DROP TABLE t
IF OBJECT_ID('trig_t_I') IS NOT NULL DROP TABLE trig_t_I
GO
CREATE TABLE t(
	id INT IDENTITY(1,1) PRIMARY KEY,
	A DECIMAL(10,2),
	B DECIMAL(10,2),
	C DECIMAL(10,2)
)
GO
-- =============================================
-- Author:		yenange
-- Create date: 2018-12-20
-- Description:	
-- =============================================
CREATE TRIGGER trig_t_I 
   ON  dbo.t 
   AFTER INSERT,UPDATE
AS 
BEGIN
	SET NOCOUNT ON;
	IF EXISTS(SELECT 1 FROM INSERTED WHERE A>0.2 AND C!=B-A)
	BEGIN
		UPDATE t 
		SET C=tt.B-tt.A
		FROM INSERTED AS tt
		WHERE t.id=tt.id AND t.A>0.2 AND t.C!=t.B-t.A
	END
END
GO
 
SET NOCOUNT ON
INSERT INTO t VALUES (0.3,5,2)
INSERT INTO t VALUES (0.1,4,1)

 
SELECT * FROM t
/*
id	A	    B	     C
--  ------  ------- ---
1	0.30	5.00	4.70
2	0.10	4.00	1.00
 */