前言：我们知道SQLSERVER清空数据表有两种方式Delete和Truncate，当然两者的不同大家也都知道(不清楚的可以MSDN)。不过这个错误“Cannot truncate table because it is being referenced by a FOREIGN KEY” 相信大家也都遇到过，解决的已解决，未解决的且看下文。
如何解决
开始我以为只要将外键Disable掉就可以了，事实证明是没用的。其实MSDN已经明确告诉了我们：
不能对以下表使用 TRUNCATE TABLE：
- 由 FOREIGN KEY 约束引用的表。（您可以截断具有引用自身的外键的表。）
- 参与索引视图的表。
- 通过使用事务复制或合并复制发布的表。
对于具有以上一个或多个特征的表，请使用 DELETE 语句。
TRUNCATE TABLE 不能激活触发器，因为该操作不记录各个行删除
难道我真的要用Delete吗？可我真的不想用Delete。原因就在于Truncate的优点，MSDN说：
与 DELETE 语句相比，TRUNCATE TABLE 具有以下优点：
- 所用的事务日志空间较少。
DELETE 语句每次删除一行，并在事务日志中为所删除的每行记录一个项。TRUNCATE TABLE 通过释放用于存储表数据的数据页来删除数据，并且在事务日志中只记录页释放。- 使用的锁通常较少。
当使用行锁执行 DELETE 语句时，将锁定表中各行以便删除。TRUNCATE TABLE 始终锁定表和页，而不是锁定各行。- 如无例外，在表中不会留有任何页。
执行 DELETE 语句后，表仍会包含空页。(略去例如)
好了，下面就来说一下解决方法。
解决方案
1.使用Delete
a) 先Delete依赖表（或叫从表）
b) 再Delete被依赖表（或叫主表）
2.使用Truncate
a) 先备份依赖表外键
b) 删除依赖表外键
c) Truncate主表
d) 重新创建依赖表外键
一段脚本
其实是一个使用Truncate进行处理的存储过程，思路见上。
USE <YOUR DB>
GO CREATE PROCEDURE [dbo].[usp_Truncate_Table]
@TableToTruncate VARCHAR(64)
AS BEGIN SET NOCOUNT ON --==变量定义
DECLARE @i int
DECLARE @Debug bit
DECLARE @Recycle bit
DECLARE @Verbose bit
DECLARE @TableName varchar(80)
DECLARE @ColumnName varchar(80)
DECLARE @ReferencedTableName varchar(80)
DECLARE @ReferencedColumnName varchar(80)
DECLARE @ConstraintName varchar(250) DECLARE @CreateStatement varchar(max)
DECLARE @DropStatement varchar(max)
DECLARE @TruncateStatement varchar(max)
DECLARE @CreateStatementTemp varchar(max)
DECLARE @DropStatementTemp varchar(max)
DECLARE @TruncateStatementTemp varchar(max)
DECLARE @Statement varchar(max) SET @Debug = 0--(0:将执行相关语句|1:不执行语句)
SET @Recycle = 0--(0:不创建/不清除存储表|1:将创建/清理存储表)
set @Verbose = 1--(1:每步执行均打印消息|0:不打印消息) SET @i = 1
SET @CreateStatement = 'ALTER TABLE [dbo].[<tablename>] WITH NOCHECK ADD CONSTRAINT [<constraintname>] FOREIGN KEY([<column>]) REFERENCES [dbo].[<reftable>] ([<refcolumn>])'
SET @DropStatement = 'ALTER TABLE [dbo].[<tablename>] DROP CONSTRAINT [<constraintname>]'
SET @TruncateStatement = 'TRUNCATE TABLE [<tablename>]' -- 创建外键临时表
IF OBJECT_ID('tempdb..#FKs') IS NOT NULL
DROP TABLE #FKs -- 获取外键
SELECT ROW_NUMBER() OVER (ORDER BY OBJECT_NAME(parent_object_id), clm1.name) as ID,
OBJECT_NAME(constraint_object_id) as ConstraintName,
OBJECT_NAME(parent_object_id) as TableName,
clm1.name as ColumnName,
OBJECT_NAME(referenced_object_id) as ReferencedTableName,
clm2.name as ReferencedColumnName
INTO #FKs
FROM sys.foreign_key_columns fk
JOIN sys.columns clm1 ON fk.parent_column_id = clm1.column_id AND fk.parent_object_id = clm1.object_id
JOIN sys.columns clm2 ON fk.referenced_column_id = clm2.column_id AND fk.referenced_object_id= clm2.object_id
--WHERE OBJECT_NAME(parent_object_id) not in ('//tables that you do not wont to be truncated')
WHERE OBJECT_NAME(referenced_object_id) = @TableToTruncate
ORDER BY OBJECT_NAME(parent_object_id) -- 外键操作(删除|重建)表
IF Not EXISTS(SELECT 1 FROM INFORMATION_SCHEMA.TABLES WHERE TABLE_NAME = 'Internal_FK_Definition_Storage')
BEGIN
IF @Verbose = 1
PRINT '1. 正在创建表(Internal_FK_Definition_Storage)...'
CREATE TABLE [Internal_FK_Definition_Storage]
(
ID int not null identity(1,1) primary key,
FK_Name varchar(250) not null,
FK_CreationStatement varchar(max) not null,
FK_DestructionStatement varchar(max) not null,
Table_TruncationStatement varchar(max) not null
)
END
ELSE
BEGIN
IF @Recycle = 0
BEGIN
IF @Verbose = 1
PRINT '1. 正在清理表(Internal_FK_Definition_Storage)...'
TRUNCATE TABLE [Internal_FK_Definition_Storage]
END
ELSE
PRINT '1. 正在清理表(Internal_FK_Definition_Storage)...'
END IF @Recycle = 0
BEGIN
IF @Verbose = 1
PRINT '2. 正在备份外键定义...'
WHILE (@i <= (SELECT MAX(ID) FROM #FKs))
BEGIN
SET @ConstraintName = (SELECT ConstraintName FROM #FKs WHERE ID = @i)
SET @TableName = (SELECT TableName FROM #FKs WHERE ID = @i)
SET @ColumnName = (SELECT ColumnName FROM #FKs WHERE ID = @i)
SET @ReferencedTableName = (SELECT ReferencedTableName FROM #FKs WHERE ID = @i)
SET @ReferencedColumnName = (SELECT ReferencedColumnName FROM #FKs WHERE ID = @i) SET @DropStatementTemp = REPLACE(REPLACE(@DropStatement,'<tablename>',@TableName),'<constraintname>',@ConstraintName)
SET @CreateStatementTemp = REPLACE(REPLACE(REPLACE(REPLACE(REPLACE(@CreateStatement,'<tablename>',@TableName),'<column>',@ColumnName),'<constraintname>',@ConstraintName),'<reftable>',@ReferencedTableName),'<refcolumn>',@ReferencedColumnName)
SET @TruncateStatementTemp = REPLACE(@TruncateStatement,'<tablename>',@TableName) INSERT INTO [Internal_FK_Definition_Storage]
SELECT @ConstraintName, @CreateStatementTemp, @DropStatementTemp, @TruncateStatementTemp SET @i = @i + 1 IF @Verbose = 1
PRINT ' > 已备份外键:[' + @ConstraintName + '] 所属表: [' + @TableName + ']'
END
END
ELSE
PRINT '2. 正在备份外键定义...' IF @Verbose = 1
PRINT '3. 正在删除外键...'
BEGIN TRAN
BEGIN TRY
SET @i = 1
WHILE (@i <= (SELECT MAX(ID) FROM [Internal_FK_Definition_Storage]))
BEGIN
SET @ConstraintName = (SELECT FK_Name FROM [Internal_FK_Definition_Storage] WHERE ID = @i)
SET @Statement = (SELECT FK_DestructionStatement FROM [Internal_FK_Definition_Storage] WITH (NOLOCK) WHERE ID = @i)
IF @Debug = 1
PRINT @Statement
ELSE
EXEC(@Statement)
SET @i = @i + 1
IF @Verbose = 1
PRINT ' > 已删除外键:[' + @ConstraintName + ']'
END IF @Verbose = 1
PRINT '4. 正在清理数据表...'
--先清除该外键所在表(由于外键所在表仍可能又被其他外键所引用，因此需要循环递归处理)(注：本处理未实现)
--请不要使用下面注释代码
/*
SET @i = 1
WHILE (@i <= (SELECT MAX(ID) FROM [Internal_FK_Definition_Storage]))
BEGIN
SET @Statement = (SELECT Table_TruncationStatement FROM [Internal_FK_Definition_Storage] WHERE ID = @i)
IF @Debug = 1
PRINT @Statement
ELSE
EXEC(@Statement)
SET @i = @i + 1
IF @Verbose = 1
PRINT ' > ' + @Statement
END
*/ IF @Debug = 1
PRINT 'TRUNCATE TABLE [' + @TableToTruncate + ']'
ELSE
EXEC('TRUNCATE TABLE [' + @TableToTruncate + ']')
IF @Verbose = 1
PRINT ' > 已清理数据表[' + @TableToTruncate + ']' IF @Verbose = 1
PRINT '5. 正在重建外键...'
SET @i = 1
WHILE (@i <= (SELECT MAX(ID) FROM [Internal_FK_Definition_Storage]))
BEGIN
SET @ConstraintName = (SELECT FK_Name FROM [Internal_FK_Definition_Storage] WHERE ID = @i)
SET @Statement = (SELECT FK_CreationStatement FROM [Internal_FK_Definition_Storage] WHERE ID = @i)
IF @Debug = 1
PRINT @Statement
ELSE
EXEC(@Statement)
SET @i = @i + 1
IF @Verbose = 1
PRINT ' > 已重建外键:[' + @ConstraintName + ']'
END
COMMIT
END TRY
BEGIN CATCH
ROLLBACK
PRINT '出错信息:'+ERROR_MESSAGE()
END CATCH
IF @Verbose = 1
PRINT '6. 处理完成！'
END
如何使用
例子说明：清空整个数据库
USE <YOUR DB>
GO --==创建临时表
IF(OBJECT_ID('TEMPDB..#TEMP')IS NOT NULL)
DROP TABLE #TEMP --==读取数据库表
SELECT SN=ROW_NUMBER()OVER(ORDER BY [name]ASC),TableName=[name]
INTO #TEMP
FROM sys.tables
WHERE [name]<>'Internal_FK_Definition_Storage' --SELECT * FROM #TEMP --==开始处理
DECLARE @ROWS INT
SELECT @ROWS=MAX(SN)FROM #TEMP
DECLARE @I INT
SET @I=1
DECLARE @TableName VARCHAR(64)
WHILE(@I<=@ROWS)
BEGIN
IF(EXISTS(SELECT 1 FROM #TEMP WHERE SN=@I))
BEGIN
SELECT @TableName=TableName FROM #TEMP WHERE SN=@I
EXEC [dbo].[usp_Truncate_Table] @TableToTruncate = @TableName
END
SET @TableName=N''
SET @I=@I+1
END
结束语：文章无甚深浅，止乎于分享。如有错误，还望斧正。