Question

默认情况下，sql server为boolean字段分配NULL值。如何告诉它使用'0'作为默认值？我尝试将默认值设置为（（0））但它仍然存在于NULL。

Answer 1

Here's a sample with a non nullable bit column with the default specified, just run the below in Management Studio:

CREATE TABLE #temp
    (
      id INT ,
      myBit BIT NOT NULL DEFAULT 0  -- not null with default of false
    );

INSERT  INTO #temp
        ( id )  -- only insert to id col, the default will set itself
VALUES  ( 123 );

INSERT INTO #temp
        ( id, myBit )
VALUES  ( 456, 1 )  -- this insert adds a true value to override the default

SELECT  *
FROM    #temp;

DROP TABLE #temp;

Produces:

id  myBit
123 0
456 1

Answer 2

ALTER TABLE 表名 ADD 列名 BIT NOT NULL DEFAULT 0;

Answer 3

I would recommend to specify default name, otherwise generated name is not telling you anything about created constraint, see sample below:

CREATE TABLE TBL_SAMPLE
(
    ID INT NOT NULL CONSTRAINT [PK_ID] PRIMARY KEY,
    BIT_COLUMN BIT NOT NULL CONSTRAINT [DF_BIT_COLUMN] DEFAULT (0)
)
GO


INSERT INTO TBL_SAMPLE (ID)
VALUES (1)
GO

SELECT * FROM TBL_SAMPLE
GO

DROP TABLE TBL_SAMPLE
GO

EDIT:

CREATE TABLE #TBL_SAMPLE 
(
    ID INT NOT NULL CONSTRAINT [PK_ID] PRIMARY KEY,
    BIT_COLUMN BIT NULL --CONSTRAINT [DF_BIT_COLUMN] DEFAULT (0) 
) 
GO


INSERT INTO #TBL_SAMPLE (ID) VALUES (1) 
GO

SELECT * FROM #TBL_SAMPLE 
GO

ALTER TABLE #TBL_SAMPLE ADD CONSTRAINT [DF_BIT_COLUMN] DEFAULT (0) FOR BIT_COLUMN 
GO


INSERT INTO #TBL_SAMPLE (ID) VALUES (2) 
INSERT INTO #TBL_SAMPLE (ID) VALUES (3) 
GO

SELECT * FROM #TBL_SAMPLE 
GO

UPDATE #TBL_SAMPLE 
SET BIT_COLUMN = 0 
WHERE BIT_COLUMN IS NULL

SELECT * FROM #TBL_SAMPLE 
GO

DROP TABLE #TBL_SAMPLE 
GO

Answer 4

ALTER TABLE（表名）ADD（列名）BIT NOT NULL默认值0；

Answer 5

请添加后缀WITH VALUES，如下所示。效果很好：

ALTER TABLE (your table) 
ADD (your column) [bit] NULL DEFAULT 1 WITH VALUES;

位类型：默认为“0”而不是NULL

5 个答案: