Question

在Microsoft SQL Server中，我知道查询是否存在列的默认约束并删除默认约束：

IF EXISTS(SELECT * FROM sysconstraints
  WHERE id=OBJECT_ID('SomeTable')
  AND COL_NAME(id,colid)='ColName'
  AND OBJECTPROPERTY(constid, 'IsDefaultCnst')=1)    
ALTER TABLE SomeTable DROP CONSTRAINT DF_SomeTable_ColName

但是由于数据库以前版本中的拼写错误，约束的名称可能是DF_SomeTable_ColName或DF_SmoeTable_ColName。

如何在没有任何SQL错误的情况下删除默认约束？缺省约束名称不会显示在INFORMATION_SCHEMA表中，这会使事情变得有点棘手。

所以，比如“删除此表/列中的默认约束”或“删除DF_SmoeTable_ColName”，但如果找不到则不会出现任何错误。

Answer 1

扩展Mitch Wheat的代码，以下脚本将生成删除约束并动态执行它的命令。

declare @schema_name nvarchar(256)
declare @table_name nvarchar(256)
declare @col_name nvarchar(256)
declare @Command  nvarchar(1000)

set @schema_name = N'MySchema'
set @table_name = N'Department'
set @col_name = N'ModifiedDate'

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.columns c on c.object_id = t.object_id and c.column_id = d.parent_column_id
 where t.name = @table_name
  and t.schema_id = schema_id(@schema_name)
  and c.name = @col_name

--print @Command

execute (@Command)

Answer 2

Rob Farley的博文可能会有所帮助：

Two ways to find / drop a default constraint without knowing its name

类似的东西：

 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

Answer 3

我发现这有效并且不使用连接：

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)

请确保columnName没有括号，因为查询正在查找完全匹配，如果是[columnName]则不会返回任何内容。

Answer 4

删除多列的约束：

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)

Answer 5

扩展解决方案（将表架构考虑在内）：

-- 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)

Answer 6

删除数据库中的所有默认约束 - 对于nvarchar（max）阈值是安全的。

/* 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

Answer 7

以下解决方案将从表中删除列的特定默认约束

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)

Answer 8

运行此命令以浏览所有约束：

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

它看起来像这样：DF__Mytable__Column__[ABC123]。然后你可以放弃约束。

Answer 9

我有一些列创建了多个默认约束，因此我创建了以下存储过程：

-v RS=

Answer 10

对于某些已创建多个 default constraints or check constraints的列有用：

修改后的https://stackoverflow.com/a/16359095/206730脚本

注意：此脚本适用于 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

Answer 11

我希望这对有类似问题的人有帮助。在ObjectExplorer窗口中，选择您的数据库=＆gt;表，=＆GT;你的桌子=＆gt;约束。如果在创建列时间定义客户，则可以看到约束的默认名称，包括列名称。然后使用：

ALTER TABLE  yourTableName DROP CONSTRAINT DF__YourTa__NewCo__47127295;

（约束名称只是一个例子）

Answer 12

在运行之前始终生成脚本并进行审核。脚本下方

positionsApplied

Answer 13

        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**

Answer 14

declare @table_name nvarchar(100)
declare @col_name nvarchar(100)
declare @constraint nvarchar(100)
set @table_name = N'TableName'
set @col_name = N'ColumnName'

IF EXISTS (select       c.*
    from        sys.columns c 
    inner join  sys.tables t on t.object_id = c.object_id
    where       t.name = @table_name
    and         c.name = @col_name) 
BEGIN

select @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 
t.name = @table_name
and c.name = @col_name

    IF LEN(ISNULL(@constraint, '')) <> 0
    BEGIN
        DECLARE @sqlcmd VARCHAR(MAX)
        SET @sqlcmd = 'ALTER TABLE ' + QUOTENAME(@table_name) + ' DROP CONSTRAINT' + 
        QUOTENAME(@constraint);
        EXEC (@sqlcmd);

    END

END
GO

Answer 15

这是我找到的最简单的解决方案。

选择表格
按 ALT + F1
滚动并查看约束名称

然后查询很简单：

std::remove_reference_t<decltype(ptr)>::element_type

https://www.sqlservergeeks.com/sql-server-dropping-a-primary-key-constraint-in-sql-server-is-it-easy-may-be-may-be-not/

如何在不知道其名称的情况下删除SQL默认约束？

15 个答案: