33

我想编写 sql 命令来删除所有表中的所有约束。我在互联网上搜索并发现以下如果数据库很小且不复杂，则可以正常工作。

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，它就不起作用。它显示了一些错误，如下所示。

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.

原因是因为某些 FK 被其他表引用。我必须运行这个脚本几次，直到数据库干净为止。

我想知道如何清除数据库中的所有 FK。

4

7 回答 7

34

有很多关于这个主题的信息。检查@AaronBertrand 的详细答案。它谈到临时禁用外键，但阅读所有内容并随意修改，您将拥有一个不错的脚本来玩并取得很多成就。

在我这边，我可以提出 2 个不同的脚本来获取所有外键。在这两种情况下，取消注释--EXEC (@SQL)以执行您的ALTER代码。或者你可以等到它打印出所有的 alter 子句，然后复制粘贴来执行它们。

第一个使用INFORMATION_SCHEMA来获取约束：

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

这个使用不同的系统视图和 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
于 2012-10-04T07:45:18.083 回答
24

这是我使用的一个简短而实用的脚本（在 SQL Server 2008 及更高版本上）来删除所有还考虑到对象架构的外键：

declare @sql nvarchar(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;
于 2016-10-12T18:50:25.727 回答
11

我已经改进了@Yaroslav 提供的第一个脚本和@Quandary 提供的脚本，因此它们现在适用于那些SQL 查询一个一个地删除所有外键的数据库超出了为SQL变量（4000或MAX字符）分配的大小。

更改后的脚本每次迭代都会删除5外键（为了安全起见，通过添加来实现TOP 5）。当没有外键可以删除时脚本停止（SQL运行后变量保持为空SELECT）。

@Yaroslav 的第一个脚本

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

@Quandary 编写的脚本

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
于 2014-11-28T23:22:56.400 回答
8

最简单的变体：

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

SELECT @sql = @sql + N'ALTER TABLE ' + QUOTENAME(KCU1.TABLE_SCHEMA) 
    + N'.' + QUOTENAME(KCU1.TABLE_NAME) 
    + N' DROP CONSTRAINT ' -- + QUOTENAME(rc.CONSTRAINT_SCHEMA)  + N'.'  -- not in MS-SQL
    + QUOTENAME(rc.CONSTRAINT_NAME) + N'; ' + CHAR(13) + CHAR(10) 
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)
于 2014-11-10T15:51:04.697 回答
3

我使用了@Yaroslav 提到的 INFORMATION_SCHEMA 解决方案，但我的数据库中有太多外键常量，无法将它们全部放入 varchar(MAX) 中。所以我不得不修改脚本以使用临时表和游标。

另外，我[]在表名周围添加了。

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;
于 2015-05-06T11:10:27.817 回答
2 
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
于 2015-09-11T13:13:18.373 回答
1

从此链接查看 Pinal 的答案，非常有帮助

https://blog.sqlauthority.com/2014/04/11/sql-server-drop-all-the-foreign-key-constraint-in-database-create-all-the-foreign-key-constraint-in-数据库/

SET NOCOUNT ON
DECLARE @table TABLE(
RowId INT PRIMARY KEY IDENTITY(1, 1),
ForeignKeyConstraintName NVARCHAR(200),
ForeignKeyConstraintTableSchema NVARCHAR(200),
ForeignKeyConstraintTableName NVARCHAR(200),
ForeignKeyConstraintColumnName NVARCHAR(200),
PrimaryKeyConstraintName NVARCHAR(200),
PrimaryKeyConstraintTableSchema NVARCHAR(200),
PrimaryKeyConstraintTableName NVARCHAR(200),
PrimaryKeyConstraintColumnName NVARCHAR(200)
)
INSERT INTO @table(ForeignKeyConstraintName, ForeignKeyConstraintTableSchema, ForeignKeyConstraintTableName, ForeignKeyConstraintColumnName)
SELECT
U.CONSTRAINT_NAME,
U.TABLE_SCHEMA,
U.TABLE_NAME,
U.COLUMN_NAME
FROM
INFORMATION_SCHEMA.KEY_COLUMN_USAGE U
INNER JOIN INFORMATION_SCHEMA.TABLE_CONSTRAINTS C
ON U.CONSTRAINT_NAME = C.CONSTRAINT_NAME
WHERE
C.CONSTRAINT_TYPE = 'FOREIGN KEY'
UPDATE @table SET
PrimaryKeyConstraintName = UNIQUE_CONSTRAINT_NAME
FROM
@table T
INNER JOIN INFORMATION_SCHEMA.REFERENTIAL_CONSTRAINTS R
ON T.ForeignKeyConstraintName = R.CONSTRAINT_NAME
UPDATE @table SET
PrimaryKeyConstraintTableSchema = TABLE_SCHEMA,
PrimaryKeyConstraintTableName = TABLE_NAME
FROM @table T
INNER JOIN INFORMATION_SCHEMA.TABLE_CONSTRAINTS C
ON T.PrimaryKeyConstraintName = C.CONSTRAINT_NAME
UPDATE @table SET
PrimaryKeyConstraintColumnName = COLUMN_NAME
FROM @table T
INNER JOIN INFORMATION_SCHEMA.KEY_COLUMN_USAGE U
ON T.PrimaryKeyConstraintName = U.CONSTRAINT_NAME
--SELECT * FROM @table
--DROP CONSTRAINT:
SELECT
'
ALTER TABLE [' + ForeignKeyConstraintTableSchema + '].[' + ForeignKeyConstraintTableName + ']
DROP CONSTRAINT [' + ForeignKeyConstraintName + ']

GO'
FROM
@table
于 2020-01-13T22:28:38.840 回答