Alter column, add default constraint
I have a table and one of the columns is "Date" of type datetime. We d开发者_开发百科ecided to add a default constraint to that column
Alter table TableName
alter column dbo.TableName.Date default getutcdate()
but this gives me error:
Incorrect syntax near '.'
Does anyone see anything obviously wrong here, which I am missing (other than having a better name for the column)
Try this
alter table TableName
add constraint df_ConstraintNAme
default getutcdate() for [Date]
example
create table bla (id int)
alter table bla add constraint dt_bla default 1 for id
insert bla default values
select * from bla
also make sure you name the default constraint..it will be a pain in the neck to drop it later because it will have one of those crazy system generated names...see also How To Name Default Constraints And How To Drop Default Constraint Without A Name In SQL Server
you can wrap reserved words in square brackets to avoid these kinds of errors:
dbo.TableName.[Date]
Actually you have to Do Like below Example, which will help to Solve the Issue...
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
I use the stored procedure below to update the defaults on a column.
It automatically removes any prior defaults on the column, before adding the new default.
Examples of usage:
-- 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''';
Stored procedure:
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
Errors this stored procedure eliminates
If you attempt to add a default to a column when one already exists, you will get the following error (something you will never see if using this stored proc):
-- 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.
I confirm like the comment from JohnH, never use column types in the your object names! It's confusing. And use brackets if possible.
Try this:
ALTER TABLE [TableName]
ADD DEFAULT (getutcdate()) FOR [Date];
You're specifying the table name twice. The ALTER TABLE part names the table. Try: Alter table TableName alter column [Date] default getutcdate()
alter table TableName drop constraint DF_TableName_WhenEntered
alter table TableName add constraint DF_TableName_WhenEntered default getutcdate() for WhenEntered
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