Question

表中有一列，应该存储Checksum列的列，但我想将其创建为此表的默认值：

CREATE TABLE tblVitalyTest (id BIGINT IDENTITY(1,1), startTime DATETIME, value1 INT, value2 INT, value3 INT, value4 DATETIME, BinCheckSum BIGINT)
GO
ALTER TABLE tblVitalyTest ADD  DEFAULT (BINARY_CHECKSUM(value1, value2, value3, value4)) FOR [BinCheckSum]
GO

所以，它应该像这样使用：

INSERT INTO tblVitalyTest (startTime,value1,value2,value3,value4) VALUES ('2015-05-25',1,1,1,'2015-11-11')

因此它应该是这样的：

id，startTime，value1，value2，value3，value4，BinCheckSum

1，“2015-05-25”，1,1,1，“2015-11-11”， 46173

但遗憾的是，表“默认”表创建失败了。

可以查询：

DECLARE @a TABLE (id BIGINT IDENTITY(1,1), startTime DATETIME, value1 INT, value2 INT, value3 INT, value4 DATETIME)

INSERT INTO @a (startTime,value1,value2,value3,value4) 
    VALUES ('2015-05-25 08:00',1,1,1,'2015-11-11'),('2015-05-25 09:00',1,2,1,'2015-11-11')
          ,('2015-05-25 10:00',null,null,null,'2015-11-11'),('2015-05-25 11:00',2,1,1,'2015-11-11'),('2015-05-25 11:00',null,null,null,'2015-11-12')

SELECT a.*,BINARY_CHECKSUM(a.value1,a.value2,a.value3,a.value4) [BinCheckSum]
FROM @a a

请告诉我有没有办法创建Binary_Checksum作为列的默认值？

Answer 1

您可以将列创建为计算列。试试这个

CREATE TABLE tblVitalyTest
 (id BIGINT IDENTITY(1,1), 
     startTime DATETIME, 
     value1 INT,
     value2 INT,
     value3 INT, 
     value4 DATETIME, 
     cksum AS BINARY_CHECKSUM(value1,value2, value3, value4 ))
    GO

或者你可以改变现有的表格

ALTER TABLE tblVitalyTest
ADD cksum AS BINARY_CHECKSUM(value1, value2, value3, value4);
GO

此查询的结果（基于您的INSERT示例）：

      select id, cksum
      from tblVitalyTest

将是：

Answer 2

基本上你不能。但你可以用触发器做类似的事情。见下文

SET ANSI_NULLS ON
GO
SET QUOTED_IDENTIFIER ON
GO

CREATE TRIGGER dbo.tblVitalyTestUpdateInsertTrigger ON dbo.tblVitalyTest
  AFTER INSERT, UPDATE
AS
  BEGIN

    SET NOCOUNT ON;
    UPDATE
      vt
    SET
      vt.BinCheckSum = BINARY_CHECKSUM(vt.value1, vt.value2, vt.value3,
                                       vt.value4)
    FROM
      dbo.tblVitalyTest vt
      INNER JOIN INSERTED i
        ON vt.id = i.id

  END
GO

TSQL BINARY_CHECKSUM作为默认值

2 个答案: