Jak zrezygnować z domyślnego ograniczenia SQL nie znając jego nazwy?

Post na blogu Roba Farleya może być pomocny:

• dwa sposoby na znalezienie / upuszczenie domyślnego ograniczenia bez znajomości jego nazwy

Coś w stylu:

 declare @table_name nvarchar(256)
 declare @col_name nvarchar(256)
 set @table_name = N'Department'
 set @col_name = N'ModifiedDate'

 select t.name, c.name, d.name, d.definition
 from 
     sys.tables t
     join sys.default_constraints d on d.parent_object_id = t.object_id
     join sys.columns c on c.object_id = t.object_id
                           and c.column_id = d.parent_column_id
 where 
     t.name = @table_name
     and c.name = @col_name

Stwierdziłem, że to działa i nie używa łączników:

DECLARE @ObjectName NVARCHAR(100)
SELECT @ObjectName = OBJECT_NAME([default_object_id]) FROM SYS.COLUMNS
WHERE [object_id] = OBJECT_ID('[tableSchema].[tableName]') AND [name] = 'columnName';
EXEC('ALTER TABLE [tableSchema].[tableName] DROP CONSTRAINT ' + @ObjectName)

Upewnij się, że nazwa kolumny nie ma nawiasów wokół niej, ponieważ zapytanie szuka dokładnego dopasowania i nie zwróci nic, jeśli jest to [nazwa kolumny].

Aby zmniejszyć ograniczenie dla wielu kolumn:

declare @table_name nvarchar(256)

declare @Command nvarchar(max) = ''

set @table_name = N'ATableName'

select @Command = @Command + 'ALTER TABLE ' + @table_name + ' drop constraint ' + d.name + CHAR(10)+ CHAR(13)
from sys.tables t
join sys.default_constraints d on d.parent_object_id = t.object_id
join sys.columns c on c.object_id = t.object_id
     and c.column_id = d.parent_column_id
where t.name = @table_name and c.name in ('column1','column2','column3')

--print @Command

execute (@Command)

Rozwiązanie Rozszerzone (uwzględnia schemat tabeli):

-- Drop default contstraint for SchemaName.TableName.ColumnName
DECLARE @schema_name NVARCHAR(256)
DECLARE @table_name NVARCHAR(256)
DECLARE @col_name NVARCHAR(256)
DECLARE @Command  NVARCHAR(1000)

set @schema_name = N'SchemaName'
set @table_name = N'TableName'
set @col_name = N'ColumnName'

SELECT @Command = 'ALTER TABLE [' + @schema_name + '].[' + @table_name + '] DROP CONSTRAINT ' + d.name
FROM sys.tables t   
JOIN sys.default_constraints d ON d.parent_object_id = t.object_id  
JOIN sys.schemas s ON s.schema_id = t.schema_id
JOIN sys.columns c ON c.object_id = t.object_id      
     AND c.column_id = d.parent_column_id
WHERE t.name = @table_name
    AND s.name = @schema_name 
    AND c.name = @col_name

EXECUTE (@Command)

Upuść wszystkie domyślne kontstrainty do bazy danych-bezpieczne dla progu nvarchar (max).

/* WARNING: THE SAMPLE BELOW; DROPS ALL THE DEFAULT CONSTRAINTS IN A DATABASE */ 
/* MAY 03, 2013 - BY WISEROOT  */
declare @table_name nvarchar(128)
declare @column_name nvarchar(128)
declare @df_name nvarchar(128)
declare @cmd nvarchar(128) 

declare table_names cursor for 
 SELECT t.name TableName, c.name ColumnName
 FROM sys.columns c INNER JOIN
     sys.tables t ON c.object_id = t.object_id INNER JOIN
     sys.schemas s ON t.schema_id = s.schema_id
     ORDER BY T.name, c.name

     open table_names
fetch next from table_names into @table_name , @column_name
while @@fetch_status = 0
BEGIN

if exists (SELECT top(1) d.name from sys.tables t join sys.default_constraints d on d.parent_object_id = t.object_id join sys.columns c on c.object_id = t.object_id and c.column_id = d.parent_column_id where t.name = @table_name and c.name = @column_name)
BEGIN
    SET @df_name = (SELECT top(1) d.name from sys.tables t join sys.default_constraints d on d.parent_object_id = t.object_id join sys.columns c on c.object_id = t.object_id and c.column_id = d.parent_column_id where t.name = @table_name and c.name = @column_name)
    select @cmd = 'ALTER TABLE [' + @table_name +  '] DROP CONSTRAINT [' +  @df_name + ']'
    print @cmd
    EXEC sp_executeSQL @cmd;
END

  fetch next from table_names into @table_name , @column_name
END

close table_names 
deallocate table_names

Następujące rozwiązanie spowoduje usunięcie określonego ograniczenia domyślnego kolumny z tabeli

Declare @Const NVARCHAR(256)

SET @Const = (
              SELECT TOP 1 'ALTER TABLE' + YOUR TABLE NAME +' DROP CONSTRAINT '+name
              FROM Sys.default_constraints A
              JOIN sysconstraints B on A.parent_object_id = B.id
              WHERE id = OBJECT_ID('YOUR TABLE NAME')
              AND COL_NAME(id, colid)='COLUMN NAME'
              AND OBJECTPROPERTY(constid,'IsDefaultCnst')=1
            )
 EXEC (@Const)

Uruchom to polecenie, aby przejrzeć wszystkie ograniczenia:

exec sp_helpconstraint 'mytable' --and look under constraint_name. 

Będzie to wyglądało mniej więcej tak: DF__Mytable__Column__[ABC123]. Wtedy możesz po prostu zrezygnować z ograniczenia.

Miałem kilka kolumn, które miały wiele domyślnych ograniczeń, więc utworzyłem następującą procedurę składowaną:

CREATE PROCEDURE [dbo].[RemoveDefaultConstraints] @table_name nvarchar(256), @column_name nvarchar(256)
AS
BEGIN

    DECLARE @ObjectName NVARCHAR(100)

    START: --Start of loop
    SELECT 
        @ObjectName = OBJECT_NAME([default_object_id]) 
    FROM 
        SYS.COLUMNS
    WHERE 
        [object_id] = OBJECT_ID(@table_name) 
        AND [name] = @column_name;

    -- Don't drop the constraint unless it exists
    IF @ObjectName IS NOT NULL
    BEGIN
        EXEC ('ALTER TABLE '+@table_name+' DROP CONSTRAINT ' + @ObjectName)
        GOTO START; --Used to loop in case of multiple default constraints
    END
END
GO

-- How to run the stored proc.  This removes the default constraint(s) for the enabled column on the User table.
EXEC [dbo].[RemoveDefaultConstraints] N'[dbo].[User]', N'enabled'
GO

-- If you hate the proc, just get rid of it
DROP PROCEDURE [dbo].[RemoveDefaultConstraints]
GO

Przydatne dla niektórych kolumn, które miały Wiele default constraints or check constraints utworzony:

Modified https://stackoverflow.com/a/16359095/206730 skrypt

Uwaga: Ten skrypt jest dla sys.check_constraints

declare @table_name nvarchar(128)
declare @column_name nvarchar(128)
declare @constraint_name nvarchar(128)
declare @constraint_definition nvarchar(512)

declare @df_name nvarchar(128)
declare @cmd nvarchar(128) 

PRINT 'DROP CONSTRAINT [Roles2016.UsersCRM].Estado'

declare constraints cursor for 
 select t.name TableName, c.name ColumnName, d.name ConstraintName, d.definition ConstraintDefinition
 from sys.tables t   
 join sys.check_constraints d  on d.parent_object_id = t.object_id  
 join sys.columns c  on c.object_id = t.object_id      
 and c.column_id = d.parent_column_id
 where t.name = N'Roles2016.UsersCRM' and c.name = N'Estado'

open constraints
fetch next from constraints into @table_name , @column_name, @constraint_name, @constraint_definition
while @@fetch_status = 0
BEGIN
    print 'CONSTRAINT: ' + @constraint_name
    select @cmd = 'ALTER TABLE [' + @table_name +  '] DROP CONSTRAINT [' +  @constraint_name + ']'
    print @cmd
    EXEC sp_executeSQL @cmd;

  fetch next from constraints into @table_name , @column_name, @constraint_name, @constraint_definition
END

close constraints 
deallocate constraints

Mam nadzieję, że to może być pomocne dla tych, którzy mają podobny problem . W oknie ObjectExplorer Wybierz swoją bazę danych=> tabele,=> twoja tabela = > ograniczenia. Jeśli klient jest zdefiniowany w czasie tworzenia kolumny, można zobaczyć domyślną nazwę ograniczenia łącznie z nazwą kolumny. następnie użyj:

ALTER TABLE  yourTableName DROP CONSTRAINT DF__YourTa__NewCo__47127295;

(Nazwa ograniczenia jest tylko przykładem)

        declare @ery nvarchar(max)
        declare @tab nvarchar(max) = 'myTable'
        declare @qu nvarchar(max) = 'alter table '+@tab+' drop constraint '

        select @ery = (select bj.name from sys.tables as tb 
        inner join sys.objects as bj 
        on tb.object_id = bj.parent_object_id
        where tb.name = @tab and bj.type = 'PK')

        exec(@qu+@ery)

       **Take a look**

Zawsze Generuj skrypt i przegląd przed uruchomieniem. Poniżej skrypt

  select 'Alter table dbo.' + t.name + ' drop constraint '+ d.name  
  from sys.tables t
  join sys.default_constraints d on d.parent_object_id = t.object_id
  join sys.columns c on c.object_id = t.object_id
       and c.column_id = d.parent_column_id
  where c.name in ('VersionEffectiveDate','VersionEndDate','VersionReasonDesc')
  order by t.name