Answers:
试试这个
alter table TableName
add constraint df_ConstraintNAme
default getutcdate() for [Date]
例
create table bla (id int)
alter table bla add constraint dt_bla default 1 for id
insert bla default values
select * from bla
还请确保您命名默认约束..稍后将其删除很麻烦,因为它将具有那些由系统生成的疯狂名称之一...另请参见如何命名默认约束和如何在不使用默认约束的情况下删除默认约束。 SQL Server中的名称
您可以将保留字括在方括号中,以避免出现此类错误:
dbo.TableName.[Date]
我使用下面的存储过程来更新列的默认设置。
在添加新默认值之前,它将自动删除该列上的所有先前默认值。
用法示例:
-- Update default to be a date.
exec [dbo].[AlterDefaultForColumn] '[dbo].[TableName]','Column','getdate()';
-- Update default to be a number.
exec [dbo].[AlterDefaultForColumn] '[dbo].[TableName]','Column,'6';
-- Update default to be a string. Note extra quotes, as this is not a function.
exec [dbo].[AlterDefaultForColumn] '[dbo].[TableName]','Column','''MyString''';
存储过程:
SET ANSI_NULLS ON
GO
SET QUOTED_IDENTIFIER ON
GO
-- Sample function calls:
--exec [dbo].[AlterDefaultForColumn] '[dbo].[TableName]','ColumnName','getdate()';
--exec [dbol].[AlterDefaultForColumn] '[dbo].[TableName]','Column,'6';
--exec [dbo].[AlterDefaultForColumn] '[dbo].[TableName]','Column','''MyString''';
create PROCEDURE [dbo].[ColumnDefaultUpdate]
(
-- Table name, including schema, e.g. '[dbo].[TableName]'
@TABLE_NAME VARCHAR(100),
-- Column name, e.g. 'ColumnName'.
@COLUMN_NAME VARCHAR(100),
-- New default, e.g. '''MyDefault''' or 'getdate()'
-- Note that if you want to set it to a string constant, the contents
-- must be surrounded by extra quotes, e.g. '''MyConstant''' not 'MyConstant'
@NEW_DEFAULT VARCHAR(100)
)
AS
BEGIN
-- Trim angle brackets so things work even if they are included.
set @COLUMN_NAME = REPLACE(@COLUMN_NAME, '[', '')
set @COLUMN_NAME = REPLACE(@COLUMN_NAME, ']', '')
print 'Table name: ' + @TABLE_NAME;
print 'Column name: ' + @COLUMN_NAME;
DECLARE @ObjectName NVARCHAR(100)
SELECT @ObjectName = OBJECT_NAME([default_object_id]) FROM SYS.COLUMNS
WHERE [object_id] = OBJECT_ID(@TABLE_NAME) AND [name] = @COLUMN_NAME;
IF @ObjectName <> ''
begin
print 'Removed default: ' + @ObjectName;
--print('ALTER TABLE ' + @TABLE_NAME + ' DROP CONSTRAINT ' + @ObjectName)
EXEC('ALTER TABLE ' + @TABLE_NAME + ' DROP CONSTRAINT ' + @ObjectName)
end
EXEC('ALTER TABLE ' + @TABLE_NAME + ' ADD DEFAULT (' + @NEW_DEFAULT + ') FOR ' + @COLUMN_NAME)
--print('ALTER TABLE ' + @TABLE_NAME + ' ADD DEFAULT (' + @NEW_DEFAULT + ') FOR ' + @COLUMN_NAME)
print 'Added default of: ' + @NEW_DEFAULT;
END
此存储过程消除的错误
如果您尝试在已经存在的列中添加默认值,则会收到以下错误(如果使用此存储过程,将永远看不到):
-- Using the stored procedure eliminates this error:
Msg 1781, Level 16, State 1, Line 1
Column already has a DEFAULT bound to it.
Msg 1750, Level 16, State 0, Line 1
Could not create constraint. See previous errors.
实际上,您必须在下面的示例中做“喜欢”,这将有助于解决问题...
drop table ABC_table
create table ABC_table
(
names varchar(20),
age int
)
ALTER TABLE ABC_table
ADD CONSTRAINT MyConstraintName
DEFAULT 'This is not NULL' FOR names
insert into ABC(age) values(10)
select * from ABC
您要两次指定表名。ALTER TABLE部件为表命名。尝试:更改表TableName更改列[日期]默认getutcdate()
更改表TableName放置约束DF_TableName_WhenEntered
更改表TableName添加约束DF_TableName_WhenEntered的默认getutcdate()