如何删除所有表中的所有外键约束？

Question

我想编写sql命令删除所有表中的所有约束。我在互联网上搜索，发现以下工作正常，如果数据库很小，并不复杂。

DECLARE @name VARCHAR(128) 
DECLARE @constraint VARCHAR(254) 
DECLARE @SQL VARCHAR(254) 
DECLARE @schema VARCHAR(128) 

SELECT @name = (SELECT TOP 1 TABLE_NAME FROM INFORMATION_SCHEMA.TABLE_CONSTRAINTS WHERE constraint_catalog=DB_NAME() AND CONSTRAINT_TYPE = 'FOREIGN KEY' ORDER BY TABLE_NAME) 
SELECT @schema = (SELECT TOP 1 schema_name(schema_id) FROM sys.objects WHERE [name] = @name) 

WHILE @name is not null 
BEGIN 
    SELECT @constraint = (SELECT TOP 1 CONSTRAINT_NAME FROM INFORMATION_SCHEMA.TABLE_CONSTRAINTS WHERE constraint_catalog=DB_NAME() AND CONSTRAINT_TYPE = 'FOREIGN KEY' AND TABLE_NAME = @name ORDER BY CONSTRAINT_NAME) 
    WHILE @constraint IS NOT NULL 
    BEGIN 
     SELECT @SQL = 'ALTER TABLE ' + @schema + '.[' + RTRIM(@name) +'] DROP CONSTRAINT [' + RTRIM(@constraint) +']' 
     EXEC (@SQL) 
     PRINT 'Dropped FK Constraint: ' + @constraint + ' on ' + @name 
     SELECT @constraint = (SELECT TOP 1 CONSTRAINT_NAME FROM INFORMATION_SCHEMA.TABLE_CONSTRAINTS WHERE constraint_catalog=DB_NAME() AND CONSTRAINT_TYPE = 'FOREIGN KEY' AND CONSTRAINT_NAME <> @constraint AND TABLE_NAME = @name ORDER BY CONSTRAINT_NAME) 
    END 
SELECT @name = (SELECT TOP 1 TABLE_NAME FROM INFORMATION_SCHEMA.TABLE_CONSTRAINTS WHERE constraint_catalog=DB_NAME() AND CONSTRAINT_TYPE = 'FOREIGN KEY' ORDER BY TABLE_NAME) 
SELECT @schema = (SELECT TOP 1 schema_name(schema_id) FROM sys.objects WHERE [name] = @name) 
END 
GO 

如果我用更复杂的数据库甚至AdventureWork运行它，它不起作用。它显示了一些像下面这样的错误。

Msg 3728, Level 16, State 1, Line 1 
'FK_ap_invoice_modification_type_id' is not a constraint. 
Msg 3727, Level 16, State 0, Line 1 
Could not drop constraint. See previous errors. 
Msg 3725, Level 16, State 0, Line 1 
The constraint 'PK_ap_invoice' is being referenced by table '_drop_now_ap_invoice_detail', foreign key constraint 'FK_ap_invoice_detail_ap_invoice'. 
Msg 3727, Level 16, State 0, Line 1 
Could not drop constraint. See previous errors. 

原因是因为一些FKs被其他表引用。我必须运行这个脚本几次，直到数据库干净。

我想知道如何清除数据库中的所有FK。

Answer 1

有很多关于这个问题的信息。通过@AaronBertrand检查this detailed answer。它讨论了暂时禁用外键，但是全部阅读并随意修改，你将会有一个很好的脚本来玩并取得很多成果。

从我这边我可以提出2个不同的脚本来获得所有外键。在两种情况下取​​消注释--EXEC (@SQL)以执行您的ALTER代码。或者你可以等到它打印所有的alter子句，然后复制粘贴来执行它们。

第一个使用的INFORMATION_SCHEMA得到约束：

DECLARE @SQL VARCHAR(MAX)='' 
SELECT @SQL = @SQL + 'ALTER TABLE ' + QUOTENAME(FK.TABLE_SCHEMA) + '.' + QUOTENAME(FK.TABLE_NAME) + ' DROP CONSTRAINT [' + RTRIM(C.CONSTRAINT_NAME) +'];' + CHAR(13) 
--SELECT K_Table = FK.TABLE_NAME, FK_Column = CU.COLUMN_NAME, PK_Table = PK.TABLE_NAME, PK_Column = PT.COLUMN_NAME, Constraint_Name = C.CONSTRAINT_NAME 
    FROM INFORMATION_SCHEMA.REFERENTIAL_CONSTRAINTS C 
INNER JOIN INFORMATION_SCHEMA.TABLE_CONSTRAINTS FK 
    ON C.CONSTRAINT_NAME = FK.CONSTRAINT_NAME 
INNER JOIN INFORMATION_SCHEMA.TABLE_CONSTRAINTS PK 
    ON C.UNIQUE_CONSTRAINT_NAME = PK.CONSTRAINT_NAME 
INNER JOIN INFORMATION_SCHEMA.KEY_COLUMN_USAGE CU 
    ON C.CONSTRAINT_NAME = CU.CONSTRAINT_NAME 
INNER JOIN (
      SELECT i1.TABLE_NAME, i2.COLUMN_NAME 
       FROM INFORMATION_SCHEMA.TABLE_CONSTRAINTS i1 
      INNER JOIN INFORMATION_SCHEMA.KEY_COLUMN_USAGE i2 
       ON i1.CONSTRAINT_NAME = i2.CONSTRAINT_NAME 
      WHERE i1.CONSTRAINT_TYPE = 'PRIMARY KEY' 
      ) PT 
    ON PT.TABLE_NAME = PK.TABLE_NAME 

--EXEC (@SQL) 

PRINT @SQL 

这一个使用不同的系统的意见和CTE表。

DECLARE @SQL varchar(4000)='' 
;WITH ReferencingFK AS 
(
    SELECT fk.Name AS 'FKName', OBJECT_NAME(fk.parent_object_id) 'ParentTable', 
      cpa.name 'ParentColumnName', OBJECT_NAME(fk.referenced_object_id) 'ReferencedTable', 
      cref.name 'ReferencedColumnName' 
    FROM sys.foreign_keys fk 
    INNER JOIN sys.foreign_key_columns fkc ON fkc.constraint_object_id = fk.object_id 
    INNER JOIN sys.columns cpa ON fkc.parent_object_id = cpa.object_id AND fkc.parent_column_id = cpa.column_id 
    INNER JOIN sys.columns cref ON fkc.referenced_object_id = cref.object_id AND fkc.referenced_column_id = cref.column_id 
) 
SELECT @SQL = @SQL + 'ALTER TABLE ' + ParentTable + ' DROP CONSTRAINT [' + RTRIM(FKName) +'];' + CHAR(13) 
--SELECT FKName, ParentTable, ParentColumnName, ReferencedTable, ReferencedColumnName 
    FROM ReferencingFK 
WHERE ReferencedTable = 'Employee' 
ORDER BY ParentTable, ReferencedTable, FKName 

--EXEC (@SQL) 

PRINT @SQL 

Answer 2

最简单的变体：

DECLARE @sql nvarchar(MAX) 
SET @sql = '' 

SELECT @sql = @sql + 'ALTER TABLE ' + QUOTENAME(RC.CONSTRAINT_SCHEMA) 
    + '.' + QUOTENAME(KCU1.TABLE_NAME) 
    + ' DROP CONSTRAINT ' + QUOTENAME(rc.CONSTRAINT_NAME) + '; ' 
FROM INFORMATION_SCHEMA.REFERENTIAL_CONSTRAINTS AS RC 

INNER JOIN INFORMATION_SCHEMA.KEY_COLUMN_USAGE AS KCU1 
    ON KCU1.CONSTRAINT_CATALOG = RC.CONSTRAINT_CATALOG 
    AND KCU1.CONSTRAINT_SCHEMA = RC.CONSTRAINT_SCHEMA 
    AND KCU1.CONSTRAINT_NAME = RC.CONSTRAINT_NAME 


-- PRINT @sql 
EXECUTE(@sql) 

Answer 3

我已经通过改进和@Yaroslav由@Quandary提供的脚本提供的第一个脚本，使他们现在适用于数据库，其SQL查询来删除所有外键一个由一个超过分配给SQL变量（4000或MAX字符）的大小。

修改后的脚本每次迭代都会删除5外键（为了安全起见，通过添加TOP 5来实现）。当没有外键丢失时，脚本停止（在运行SELECT后SQL变量保持为空）。

第一个脚本由@Yaroslav

DECLARE @SQL varchar(4000) 
IterationStart: 
SET @SQL='' 
SELECT TOP 5 @SQL = @SQL + 'ALTER TABLE ' + FK.TABLE_NAME + ' DROP CONSTRAINT [' + RTRIM(C.CONSTRAINT_NAME) +'];' + CHAR(13) 
    FROM INFORMATION_SCHEMA.REFERENTIAL_CONSTRAINTS C 
INNER JOIN INFORMATION_SCHEMA.TABLE_CONSTRAINTS FK 
    ON C.CONSTRAINT_NAME = FK.CONSTRAINT_NAME 
INNER JOIN INFORMATION_SCHEMA.TABLE_CONSTRAINTS PK 
    ON C.UNIQUE_CONSTRAINT_NAME = PK.CONSTRAINT_NAME 
INNER JOIN INFORMATION_SCHEMA.KEY_COLUMN_USAGE CU 
    ON C.CONSTRAINT_NAME = CU.CONSTRAINT_NAME 
INNER JOIN (
      SELECT i1.TABLE_NAME, i2.COLUMN_NAME 
       FROM INFORMATION_SCHEMA.TABLE_CONSTRAINTS i1 
      INNER JOIN INFORMATION_SCHEMA.KEY_COLUMN_USAGE i2 
       ON i1.CONSTRAINT_NAME = i2.CONSTRAINT_NAME 
      WHERE i1.CONSTRAINT_TYPE = 'PRIMARY KEY' 
      ) PT 
    ON PT.TABLE_NAME = PK.TABLE_NAME 
IF @SQL <> '' 
BEGIN 
    EXEC(@SQL) 
    GOTO IterationStart 
END 

脚本由@Quandary

DECLARE @sql nvarchar(MAX) 

IterationStart: 
SET @sql = '' 

SELECT TOP 5 @sql = @sql + 'ALTER TABLE ' + QUOTENAME(RC.CONSTRAINT_SCHEMA) 
    + '.' + QUOTENAME(KCU1.TABLE_NAME) 
    + ' DROP CONSTRAINT ' + QUOTENAME(rc.CONSTRAINT_NAME) + '; ' 
FROM INFORMATION_SCHEMA.REFERENTIAL_CONSTRAINTS AS RC 

INNER JOIN INFORMATION_SCHEMA.KEY_COLUMN_USAGE AS KCU1 
    ON KCU1.CONSTRAINT_CATALOG = RC.CONSTRAINT_CATALOG 
    AND KCU1.CONSTRAINT_SCHEMA = RC.CONSTRAINT_SCHEMA 
    AND KCU1.CONSTRAINT_NAME = RC.CONSTRAINT_NAME 

IF @SQL <> '' 
BEGIN 
    EXEC(@SQL) 
    GOTO IterationStart 
END 

Answer 4

我使用@Yaroslav提到INFORMATION_SCHEMA解决方案，但有太多的外键的常量在我的数据库，以适应他们全部转换成varchar（MAX）。所以我不得不修改脚本来使用临时表和光标。

另外，我在表名的周围加了[]。

DECLARE @SQL TABLE (Command VARCHAR(MAX)) 

INSERT @SQL 
SELECT 'ALTER TABLE [' + FK.TABLE_NAME + '] DROP CONSTRAINT [' + RTRIM(C.CONSTRAINT_NAME) +'];' + CHAR(13) 
    FROM INFORMATION_SCHEMA.REFERENTIAL_CONSTRAINTS C 
INNER JOIN INFORMATION_SCHEMA.TABLE_CONSTRAINTS FK 
    ON C.CONSTRAINT_NAME = FK.CONSTRAINT_NAME 
INNER JOIN INFORMATION_SCHEMA.TABLE_CONSTRAINTS PK 
    ON C.UNIQUE_CONSTRAINT_NAME = PK.CONSTRAINT_NAME 
INNER JOIN INFORMATION_SCHEMA.KEY_COLUMN_USAGE CU 
    ON C.CONSTRAINT_NAME = CU.CONSTRAINT_NAME 
INNER JOIN (
      SELECT i1.TABLE_NAME, i2.COLUMN_NAME 
       FROM INFORMATION_SCHEMA.TABLE_CONSTRAINTS i1 
      INNER JOIN INFORMATION_SCHEMA.KEY_COLUMN_USAGE i2 
       ON i1.CONSTRAINT_NAME = i2.CONSTRAINT_NAME 
      WHERE i1.CONSTRAINT_TYPE = 'PRIMARY KEY' 
      ) PT 
    ON PT.TABLE_NAME = PK.TABLE_NAME 

DECLARE cmdCursor CURSOR 
    FOR SELECT Command FROM @SQL 
OPEN cmdCursor 
DECLARE @Command VARCHAR(MAX) 

FETCH NEXT FROM cmdCursor INTO @Command 
WHILE @@FETCH_STATUS = 0 
BEGIN 
    PRINT @Command 
    EXEC (@Command) 
    FETCH NEXT FROM cmdCursor INTO @Command 
END 

CLOSE cmdCursor; 
DEALLOCATE cmdCursor; 

Answer 5

CREATE TABLE #Commands (Command VARCHAR(MAX)) 

INSERT #Commands 
SELECT 'ALTER TABLE ' + QUOTENAME(RC.CONSTRAINT_SCHEMA) 
    + '.' + QUOTENAME(KCU1.TABLE_NAME) 
    + ' DROP CONSTRAINT ' + QUOTENAME(rc.CONSTRAINT_NAME) + '; ' 
FROM INFORMATION_SCHEMA.REFERENTIAL_CONSTRAINTS AS RC 

INNER JOIN INFORMATION_SCHEMA.KEY_COLUMN_USAGE AS KCU1 
    ON KCU1.CONSTRAINT_CATALOG = RC.CONSTRAINT_CATALOG 
    AND KCU1.CONSTRAINT_SCHEMA = RC.CONSTRAINT_SCHEMA 
    AND KCU1.CONSTRAINT_NAME = RC.CONSTRAINT_NAME 
WHERE ORDINAL_POSITION=1 

--SELECT * FROM #Commands 

DECLARE @Command VARCHAR(MAX) 
DECLARE curCommand CURSOR FOR 
SELECT Command FROM #Commands 

OPEN curCommand 

FETCH NEXT FROM curCommand INTO @Command 

WHILE @@FETCH_STATUS =0 
BEGIN 

    EXEC(@Command) 
    FETCH NEXT FROM curCommand INTO @Command 

END 

CLOSE curCommand 
DEALLOCATE curCommand 

DROP TABLE #Commands 

Answer 6

这里有一个简短而亲切的脚本我使用（SQL Server 2008和高达上），以去除所有的外键也考虑到对象的架构：

declare @sql varchar(max) = (
    select 
     'alter table ' + quotename(schema_name(schema_id)) + '.' + 
     quotename(object_name(parent_object_id)) + 
     ' drop constraint '+quotename(name) + ';' 
    from sys.foreign_keys 
    for xml path('') 
); 
exec sp_executesql @sql;