Question

我有以下内容：

DROP TABLE [dbo].[ExtraUserInformation];
DROP TABLE [dbo].[UserProfile];
DROP TABLE [dbo].[webpages_Membership];
DROP TABLE [dbo].[webpages_OAuthMembership];
DROP TABLE [dbo].[webpages_Roles];
DROP TABLE [dbo].[webpages_UsersInRoles];

CREATE TABLE [dbo].[ExtraUserInformation] (
    [Id]       INT            IDENTITY (1, 1) NOT NULL,
    [UserId]   INT            NOT NULL,
    [FullName] NVARCHAR (MAX) NULL,
    [Link]     NVARCHAR (MAX) NULL,
    [Verified] BIT            NULL,
    CONSTRAINT [PK_dbo.ExtraUserInformation] PRIMARY KEY CLUSTERED ([Id] ASC)
);

CREATE TABLE [dbo].[webpages_UsersInRoles] (
    [UserId] INT NOT NULL,
    [RoleId] INT NOT NULL,
    PRIMARY KEY CLUSTERED ([UserId] ASC, [RoleId] ASC),
    CONSTRAINT [fk_UserId] FOREIGN KEY ([UserId]) REFERENCES [dbo].[UserProfile] ([UserId]),
    CONSTRAINT [fk_RoleId] FOREIGN KEY ([RoleId]) REFERENCES [dbo].[webpages_Roles] ([RoleId])
);

然而，这是失败的消息说：

Msg 3726, Level 16, State 1, Line 6
Could not drop object 'dbo.UserProfile' because it is referenced by a FOREIGN KEY constraint.
Msg 3726, Level 16, State 1, Line 9
Could not drop object 'dbo.webpages_Roles' because it is referenced by a FOREIGN KEY constraint.
Msg 2714, Level 16, State 6, Line 27
There is already an object named 'UserProfile' in the database.
Checking identity information: current identity value 'NULL', current column value 'NULL'.
DBCC execution completed. If DBCC printed error messages, contact your system administrator.

在这种情况下如何删除表格？

Answer 1

您必须先删除约束，然后才能删除该表。否则，违反规则。如何获得外键关系看到这个老问题。 SQL DROP TABLE foreign key constraint

Answer 2

1 - 首先，在删除表之后删除外键约束。

2 - 您可以通过执行以下查询来删除所有外键：

DECLARE @SQL varchar(4000)=''
SELECT @SQL = 
@SQL + 'ALTER TABLE ' + s.name+'.'+t.name + ' DROP CONSTRAINT [' + RTRIM(f.name) +'];' + CHAR(13)
FROM sys.Tables t
INNER JOIN sys.foreign_keys f ON f.parent_object_id = t.object_id
INNER JOIN sys.schemas     s ON s.schema_id = f.schema_id

--EXEC (@SQL)

PRINT @SQL

如果执行打印结果@SQL，外键将被删除。

Answer 3

删除包含外部约束的表的最佳答案是：

步骤1：删除表的主键。
步骤2：现在它将提示是否删除所有外来引用。
第3步：删除表格。

Answer 4

您必须在删除表之前删除约束。

您可以使用这些查询查找表中的所有FK，并在使用表格的表格中找到FK。

Declare @SchemaName VarChar(200) = 'Your Schema name'
Declare @TableName VarChar(200) = 'Your Table Name'

-- Find FK in This table.
SELECT 
    ' IF  EXISTS (SELECT * FROM sys.foreign_keys WHERE object_id = 
OBJECT_ID(N''' + 
      '[' + OBJECT_SCHEMA_NAME(FK.parent_object_id) + '].[' + FK.name + ']'
+ ''') AND parent_object_id = OBJECT_ID(N''' + 
      '[' + OBJECT_SCHEMA_NAME(FK.parent_object_id) + '].[' + 
OBJECT_NAME(FK.parent_object_id) + ']' + ''')) ' +

    'ALTER TABLE ' +  OBJECT_SCHEMA_NAME(FK.parent_object_id) +
    '.[' + OBJECT_NAME(FK.parent_object_id) + 
    '] DROP CONSTRAINT ' + FK.name
    , S.name , O.name, OBJECT_NAME(FK.parent_object_id)
FROM sys.foreign_keys AS FK
INNER JOIN Sys.objects As O 
  ON (O.object_id = FK.parent_object_id )
INNER JOIN SYS.schemas AS S 
  ON (O.schema_id = S.schema_id)  
WHERE 
      O.name = @TableName
      And S.name = @SchemaName


-- Find the FKs in the tables in which this table is used
  SELECT 
    ' IF  EXISTS (SELECT * FROM sys.foreign_keys WHERE object_id =   
      OBJECT_ID(N''' + 
      '[' + OBJECT_SCHEMA_NAME(FK.parent_object_id) + '].[' + FK.name + ']'
  + ''') AND parent_object_id = OBJECT_ID(N''' + 
      '[' + OBJECT_SCHEMA_NAME(FK.parent_object_id) + '].[' + 
 OBJECT_NAME(FK.parent_object_id) + ']' + ''')) ' +

    ' ALTER TABLE ' +  OBJECT_SCHEMA_NAME(FK.parent_object_id) +
    '.[' + OBJECT_NAME(FK.parent_object_id) + 
    '] DROP CONSTRAINT ' + FK.name
    , S.name , O.name, OBJECT_NAME(FK.parent_object_id)
FROM sys.foreign_keys AS FK
INNER JOIN Sys.objects As O 
  ON (O.object_id = FK.referenced_object_id )
INNER JOIN SYS.schemas AS S 
  ON (O.schema_id = S.schema_id)  
WHERE 
      O.name = @TableName
      And S.name = @SchemaName

Answer 5

BhupeshC and murat，这就是我想要的。但是@SQL varchar（4000）还不够大。所以，小改变

DECLARE @cmd varchar(4000)

DECLARE MY_CURSOR CURSOR 
  LOCAL STATIC READ_ONLY FORWARD_ONLY
FOR 

select 'ALTER TABLE ['+s.name+'].['+t.name+'] DROP CONSTRAINT [' + RTRIM(f.name) +'];' FROM sys.Tables t INNER JOIN sys.foreign_keys f ON f.parent_object_id = t.object_id INNER JOIN sys.schemas s ON s.schema_id = f.schema_id

OPEN MY_CURSOR
FETCH NEXT FROM MY_CURSOR INTO @cmd
WHILE @@FETCH_STATUS = 0
BEGIN
    -- EXEC (@cmd)
    PRINT @cmd
    FETCH NEXT FROM MY_CURSOR INTO @cmd
END
CLOSE MY_CURSOR
DEALLOCATE MY_CURSOR

GO

Answer 6

    --Find and drop the constraints

    DECLARE @dynamicSQL VARCHAR(MAX)
    DECLARE MY_CURSOR CURSOR 

    LOCAL STATIC READ_ONLY FORWARD_ONLY 
    FOR
        SELECT dynamicSQL = 'ALTER TABLE [' +  OBJECT_SCHEMA_NAME(parent_object_id) + '].[' + OBJECT_NAME(parent_object_id) + '] DROP CONSTRAINT [' + name + ']'
        FROM sys.foreign_keys
        WHERE object_name(referenced_object_id)  in ('table1', 'table2', 'table3')
    OPEN MY_CURSOR
    FETCH NEXT FROM MY_CURSOR INTO @dynamicSQL
    WHILE @@FETCH_STATUS = 0
    BEGIN

        PRINT @dynamicSQL
        EXEC (@dynamicSQL)

        FETCH NEXT FROM MY_CURSOR INTO @dynamicSQL
    END
    CLOSE MY_CURSOR
    DEALLOCATE MY_CURSOR


    -- Drop tables
    DROP 'table1'
    DROP 'table2'
    DROP 'table3'

Answer 7

如果MySQL服务器中存在外键约束，则删除表吗？

运行sql查询：

SET FOREIGN_KEY_CHECKS = 0; DROP TABLE table_name

希望它有所帮助！

Answer 8

输入此内容.... SET foreign_key_checks = 0;
删除您的表格，然后输入SET foreign_key_checks = 1;

MySQL – Temporarily disable Foreign Key Checks or Constraints

如果SQL Server中存在外键约束，如何删除表？

8 个答案: