Alter "Default" in SQL Server - sql-server

Question

I have custom default value in a SQL server 2008 table.
Similar to this
CREATE DEFAULT [dbo].[Default_Timestamp]
AS
GetDate()
Now I want to change the value in that default.
CREATE DEFAULT [dbo].[Default_Timestamp]
AS
GETUTCDATE()
Before I can edit the existing one, I need to drop the first one and recreate it.
DROP DEFAULT [dbo].[Default_Timestamp]
it gives following error.
Msg 3716, Level 16, State 3, Line 4
The default 'dbo.Default_Timestamp' cannot be dropped because it is bound to one or more column.
Since the default is already use by few tables I cannot drop and recreate a new one.
I know I need to unbind all the tables from this default before I can recreate it.
Can anyone provide a script to list all the table and columns which are bound with that default?

Answer 1

It's a multi-step process:
1) Find the object_id for your default :
DECLARE #DefaultObjectID INT
SELECT #DefaultObjectID = OBJECT_ID('Default_Timestamp')
2) Find all the columns that reference that default:
SELECT
ColumnName = c.Name,
TableName = t.Name,
UnbindCmd = 'EXEC sp_unbindefault ''' + t.Name + '.' + c.name + ''''
FROM sys.columns c
INNER JOIN sys.tables t ON c.object_id = t.object_id
WHERE default_object_id = #DefaultObjectID
This will produce a list of UnbindCmd commands to actually remove the DEFAULT from those columns.
3) Now, copy that column from your SQL Server Mgmt Studio window, and execute it in a new query window to actually "unbind" the default from all those columns
4) Now define your new default
However: these days, I would probably not define a new DEFAULT per se - can't you just set the default constraint on the columns in question directly?
ALTER TABLE dbo.YourTable
ADD CONSTRAINT DF_YourTable_TimeStamp
DEFAULT GETUTCDATE() FOR YourColumnName
Seems a like easier to work with going into the future! When you explicitly name your constraint, you can also easily find and drop that constraint again, if need be.

Answer 2

I ran across this issue when I found some old style defaults in my database where I had to update uses_ansi_nulls and uses_quoted_identifier en mass in my database.
Here is the code that I ended up writing to replace the old style defaults (CREATE DEFAULT sp_BindDefault) with the newer style (ALTER TABLE).
DECLARE #strSQL varchar(max)
, #DBName varchar(50) = DB_NAME();
DROP TABLE IF EXISTS #tmp;
SELECT IDENTITY(int, 1,1) AS ID,
UnbindCmd = 'EXEC sp_unbindefault ''' + t.Name + '.' + c.name + ''';',
DropCmd = 'DROP DEFAULT IF EXISTS [' + SCHEMA_NAME(SO.schema_id) + '].[' + OBJECT_NAME(SO.object_id) + '];',
CreateCmd = 'ALTER TABLE [' + SCHEMA_NAME(t.Schema_id) + '].[' + t.Name + ']'
+ ' ADD CONSTRAINT df_' + REPLACE(t.Name, ' ', '') + '_' + REPLACE(c.Name, ' ', '')
+ ' DEFAULT (' + RIGHT(m.definition, LEN(m.definition) - CHARINDEX(' AS ', m.definition) - 3)
+ ') FOR ' + QUOTENAME(c.Name) + ';'
INTO #tmp
FROM sys.sql_modules m
join sys.columns c on c.default_object_id = m.object_id
INNER JOIN sys.tables t ON c.object_id = t.object_id
JOIN sys.objects SO ON SO.object_id = C.default_object_id
WHERE (m.uses_ansi_nulls = 0
OR m.uses_quoted_identifier = 0)
ORDER BY
t.name
, c.name;
BEGIN TRANSACTION
BEGIN TRY
DECLARE UnbindCursor CURSOR LOCAL FAST_FORWARD
FOR SELECT UnbindCmd
FROM #tmp
ORDER BY
ID;
OPEN UnbindCursor;
FETCH NEXT FROM UnbindCursor INTO #strSQL;
WHILE ##FETCH_STATUS = 0
BEGIN
EXEC (#strSQL);
FETCH NEXT FROM UnbindCursor INTO #strSQL;
END
CLOSE UnbindCursor;
DEALLOCATE UnbindCursor;
DECLARE DropCursor CURSOR LOCAL FAST_FORWARD
FOR SELECT DropCmd
FROM #tmp
GROUP BY
DropCmd
ORDER BY
MIN(id)
OPEN DropCursor;
FETCH NEXT FROM DropCursor INTO #strSQL;
WHILE ##FETCH_STATUS = 0
BEGIN
EXEC (#strSQL);
FETCH NEXT FROM DropCursor INTO #strSQL;
END
CLOSE DropCursor;
DEALLOCATE DropCursor;
DECLARE CreateCursor CURSOR LOCAL FAST_FORWARD
FOR SELECT CreateCmd
FROM #tmp
ORDER BY
id
OPEN CreateCursor;
FETCH NEXT FROM CreateCursor INTO #strSQL;
WHILE ##FETCH_STATUS = 0
BEGIN
EXEC (#strSQL);
FETCH NEXT FROM CreateCursor INTO #strSQL;
END
CLOSE CreateCursor;
DEALLOCATE CreateCursor;
COMMIT TRANSACTION
END TRY
BEGIN CATCH
DECLARE #ErrorMessage nvarchar(4000)
, #ErrorSeverity int
, #ErrorState int;
SELECT
#ErrorMessage = ERROR_MESSAGE(),
#ErrorSeverity = ERROR_SEVERITY(),
#ErrorState = ERROR_STATE();
IF XACT_STATE() <> 0 ROLLBACK TRANSACTION;
RAISERROR (#ErrorMessage, -- Message text.
#ErrorSeverity, -- Severity.
#ErrorState -- State.
);
END CATCH

Answer 3

I never saw CREATE DEFAULT or DROP DEFAULT as standalone commands, but only know the CONSTRAINT clause to add or drop a default constraint.
SSMS 2008 generates the following code (right click in table designer, "Generate Change Script..."):
ALTER TABLE dbo.T ADD CONSTRAINT
DF_T_DateTimeColumn DEFAULT getdate() FOR DateTimeColumn
GO
ALTER TABLE dbo.T
DROP CONSTRAINT DF_T_DateTimeColumn
GO
ALTER TABLE dbo.T ADD CONSTRAINT
DF_T_DateTimeColumn DEFAULT getutcdate() FOR DateTimeColumn
GO
update:
I admit it, I never used EXEC sp_bindefault, but I think its use is discouraged, as MSDN says:
This feature will be removed in a future version of Microsoft SQL
Server. Do not use this feature in new development work, and modify
applications that currently use this feature as soon as possible. We
recommend that you create default definitions by using the DEFAULT
keyword of the ALTER TABLE or CREATE TABLE statements instead.
This also applies to sp_unbindefault, of course.

Answer 4

You can find the columns that use a default object by looking at the default_object_id in sys.columns:
ID of the default object, regardless of whether it is a stand-alone
object sys.sp_bindefault, or an inline, column-level DEFAULT
constraint.
Knowing this is trivial to build a script that unbinds all columns from a default object and replaces the default with a constraint based default value:
use master;
go
if db_id('test') is not null
drop database test;
go
create database test;
go
use test;
go
create default foo as 1;
go
create table t1 (a int);
create table t2 (b int);
go
exec sp_bindefault 'foo', 't1.a';
exec sp_bindefault 'foo', 't2.b';
go
drop default foo;
-- Msg 3716, Level 16, State 3, Line 2
-- The default 'foo' cannot be dropped because it is bound to one or more column.
go
declare crs cursor static forward_only read_only for
select object_schema_name(object_id) as schema_name,
object_name(object_id) as object_name,
name as column_name
from sys.columns where default_object_id = object_id('foo');
open crs;
declare #schema_name sysname, #object_name sysname, #column_name sysname, #sql nvarchar(max);
fetch next from crs into #schema_name, #object_name, #column_name;
while ##fetch_status = 0
begin
set #sql = N'exec sp_unbindefault ' + quotename(
quotename(#schema_name) + N'.'+
quotename(#object_name) + N'.'+
quotename(#column_name), '''');
print #sql;
exec sp_executesql #sql;
set #sql = N'alter table ' +
quotename(#schema_name) + N'.' +
quotename(#object_name) + N' add constraint ' +
quotename(N'default_' + #column_name) + N' default 2 for ' +
quotename(#column_name);
print #sql;
exec sp_executesql #sql;
fetch next from crs into #schema_name, #object_name, #column_name;
end
close crs;
deallocate crs;
go
drop default foo;
-- it now succeeds
go