有朋友问起：MSSQL中如何用SQL清除所有表的数据？这个需求分三种类型：
第一：只要数据库中表是空的；
第二：表是空的，并且自增长列可以从１开始增长。
第三：表是空的，并且自增长列可以从１开始增长，而且存在表间的约束。
邀月稍微整理了下，放在这里，便于有需要的朋友参阅。
其实，这不算什么需求。只要用数据库的生成脚本，几分钟即可生成一个干净的表结构及存储过程、视图、约束等。这里提供了另一种用SQL解决问题的方案。权当是无聊的学习，加深点印象吧。呵呵。
首先，作一些假设：假设database名为TestDB_2000_2005_2008
预先准备一些脚本
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1. use master
2. go
3. IF OBJECT_ID('TestDB_2000_2005_2008') IS NOT NULL
4. -- print 'Exist databse!'
5. -- else print 'OK!'
6. DROP Database TestDB_2000_2005_2008
7. GO
8. Create database TestDB_2000_2005_2008
9. go
10. use TestDB_2000_2005_2008
11. go
12. IF OBJECT_ID('b') IS NOT NULL
13. drop table b
14. go
15. create table b(id int identity(1,1),ba int,bb int)
16. --truncate table b
17. insert into b
18. select 1,1 union all
19. select 2,2 union all
20. select 1,1
21. IF OBJECT_ID('c') IS NOT NULL
22. drop table c
23. go
24. create table c(id int identity(1,1),ca int,cb int)
25. insert into c
26. select 1,2 union all
27. select 1,3
use master go IF OBJECT_ID('TestDB_2000_2005_2008') IS NOT NULL -- print 'Exist databse!' -- else print 'OK!' DROP Database TestDB_2000_2005_2008 GO Create database TestDB_2000_2005_2008 go use TestDB_2000_2005_2008 go IF OBJECT_ID('b') IS NOT NULL drop table b go create table b(id int identity(1,1),ba int,bb int) --truncate table b insert into b select 1,1 union all select 2,2 union all select 1,1 IF OBJECT_ID('c') IS NOT NULL drop table c go create table c(id int identity(1,1),ca int,cb int) insert into c select 1,2 union all select 1,3
先来看看第一种需求： 只要数据库中表是空的。
这个其实并不难，用一个游标循环得出所有表名，再清除所有表，delete或truncate table
提供几个语句：以下语句均在SQL2000/SQL2005/SQL2008下使用通过。
方法甲：
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1. /********************MSSQL 2000/2005/2008***********************/
2. use TestDB_2000_2005_2008
3. go
4. select * from b
5. select * from c
6. Declare @t varchar (1024)
7. Declare @SQL varchar(2048)
8. Declare tbl_cur cursor for select TABLE_NAME from INFORMATION_SCHEMA.TABLES WHERE TABLE_TYPE = 'BASE TABLE'
9. OPEN tbl_cur FETCH NEXT from tbl_cur INTO @t
10. WHILE @@FETCH_STATUS = 0
11. BEGIN
12. SET @SQL='TRUNCATE TABLE '+ @t
13. --print (@SQL)
14. EXEC (@SQL)
15. FETCH NEXT from tbl_cur INTO @t
16. END
17. CLOSE tbl_cur
18. DEALLOCATE tbl_Cur
19. select * from b
20. select * from c
/********************MSSQL 2000/2005/2008***********************/ use TestDB_2000_2005_2008 go select * from b select * from c Declare @t varchar (1024) Declare @SQL varchar(2048) Declare tbl_cur cursor for select TABLE_NAME from INFORMATION_SCHEMA.TABLES WHERE TABLE_TYPE = 'BASE TABLE' OPEN tbl_cur FETCH NEXT from tbl_cur INTO @t WHILE @@FETCH_STATUS = 0 BEGIN SET @SQL='TRUNCATE TABLE '+ @t --print (@SQL) EXEC (@SQL) FETCH NEXT from tbl_cur INTO @t END CLOSE tbl_cur DEALLOCATE tbl_Cur select * from b select * from c
方法乙：
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1. /********************MSSQL 2000/2005/2008***********************/
2. use TestDB_2000_2005_2008
3. go
4. select * from b
5. select * from c
6. select * from d
7. select * from e
8. DECLARE @TableName VARCHAR(256)
9. DECLARE @varSQL VARCHAR(512)
10. DECLARE @getTBName CURSOR SET @getTBName = CURSOR FOR SELECT name FROM sys.Tables WHERE NAME NOT LIKE 'Category'
11. OPEN @getTBName FETCH NEXT FROM @getTBName INTO @TableName
12. WHILE @@FETCH_STATUS = 0
13. BEGIN
14. SET @varSQL = 'Truncate table '+ @TableName
15. --PRINT (@varSQL)
16. EXEC (@varSQL)
17. FETCH NEXT FROM @getTBName INTO @TableName
18. END
19. CLOSE @getTBName
20. DEALLOCATE @getTBName
21. ----select * from b
22. ----select * from c
/********************MSSQL 2000/2005/2008***********************/ use TestDB_2000_2005_2008 go select * from b select * from c select * from d select * from e DECLARE @TableName VARCHAR(256) DECLARE @varSQL VARCHAR(512) DECLARE @getTBName CURSOR SET @getTBName = CURSOR FOR SELECT name FROM sys.Tables WHERE NAME NOT LIKE 'Category' OPEN @getTBName FETCH NEXT FROM @getTBName INTO @TableName WHILE @@FETCH_STATUS = 0 BEGIN SET @varSQL = 'Truncate table '+ @TableName --PRINT (@varSQL) EXEC (@varSQL) FETCH NEXT FROM @getTBName INTO @TableName END CLOSE @getTBName DEALLOCATE @getTBName ----select * from b ----select * from c
方法丙：
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1. Declare @t table(query varchar(2000),tables varchar(100))
2. Insert into @t
3. select 'Truncate table ['+T.table_name+']', T.Table_Name from INFORMATION_SCHEMA.TABLES T
4. left outer join INFORMATION_SCHEMA.TABLE_CONSTRAINTS TC
5. on T.table_name=TC.table_name
6. where (TC.constraint_Type ='Foreign Key' or TC.constraint_Type is NULL) and
7. T.table_name not in ('dtproperties','sysconstraints','syssegments') and
8. Table_type='BASE TABLE'
9. Insert into @t
10. select 'delete from ['+T.table_name+']', T.Table_Name from INFORMATION_SCHEMA.TABLES T
11. left outer join INFORMATION_SCHEMA.TABLE_CONSTRAINTS TC
12. on T.table_name=TC.table_name where TC.constraint_Type ='Primary Key' and T.table_name <>'dtproperties'and Table_type='BASE TABLE'
13. Declare @sql varchar(8000)
14. Select @sql=IsNull(@sql+' ','')+ query from @t
15. print(@sql)
16. Exec(@sql)
Declare @t table(query varchar(2000),tables varchar(100)) Insert into @t select 'Truncate table ['+T.table_name+']', T.Table_Name from INFORMATION_SCHEMA.TABLES T left outer join INFORMATION_SCHEMA.TABLE_CONSTRAINTS TC on T.table_name=TC.table_name where (TC.constraint_Type ='Foreign Key' or TC.constraint_Type is NULL) and T.table_name not in ('dtproperties','sysconstraints','syssegments') and Table_type='BASE TABLE' Insert into @t select 'delete from ['+T.table_name+']', T.Table_Name from INFORMATION_SCHEMA.TABLES T left outer join INFORMATION_SCHEMA.TABLE_CONSTRAINTS TC on T.table_name=TC.table_name where TC.constraint_Type ='Primary Key' and T.table_name <>'dtproperties'and Table_type='BASE TABLE' Declare @sql varchar(8000) Select @sql=IsNull(@sql+' ','')+ query from @t print(@sql) Exec(@sql)
再来看看第二种需求： 表是空的，并且自增长列可以从１开始增长 。
这种需求其实和第一种差不多。 因为我们在以上语句中使用的是 truncate table 语句，所以，表的自增长 列是默认从头重新的。
关键是第三种需求： 表是空的，并且自增长列可以从１开始增长 ，而且存在表间的约束 。
这是个比较头痛的问题。因为外键约束，不能使用truncate table语句，但是，如果使用delete，又不能使自增长列从１开始重排。
我们不妨先来增加一些约束条件：
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1. CREATE TABLE [d] (
2. [id] [int] IDENTITY (1, 1) NOT NULL ,
3. [da] [int] NULL ,
4. [db] [int] NULL ,
5. CONSTRAINT [PK_d] PRIMARY KEY CLUSTERED
6. (
7. [id]
8. ) ON [PRIMARY]
9. ) ON [PRIMARY]
10. CREATE TABLE [e] (
11. [id] [int] IDENTITY (1, 1) NOT NULL ,
12. [da] [int] NULL ,
13. [db] [int] NULL ,
14. [did] [int] NULL ,
15. CONSTRAINT [FK_e_d] FOREIGN KEY
16. (
17. [did]
18. ) REFERENCES [d] (
19. [id]
20. )
21. ) ON [PRIMARY]
22. insert into d
23. select 5,6 union all
24. select 7,8 union all
25. select 9,9
26. insert into e
27. select 8,6,1 union all
28. select 8,8,2 union all
29. select 8,9,2
CREATE TABLE [d] ( [id] [int] IDENTITY (1, 1) NOT NULL , [da] [int] NULL , [db] [int] NULL , CONSTRAINT [PK_d] PRIMARY KEY CLUSTERED ( [id] ) ON [PRIMARY] ) ON [PRIMARY] CREATE TABLE [e] ( [id] [int] IDENTITY (1, 1) NOT NULL , [da] [int] NULL , [db] [int] NULL , [did] [int] NULL , CONSTRAINT [FK_e_d] FOREIGN KEY ( [did] ) REFERENCES [d] ( [id] ) ) ON [PRIMARY] insert into d select 5,6 union all select 7,8 union all select 9,9 insert into e select 8,6,1 union all select 8,8,2 union all select 8,9,2
此时再来执行甲乙丙语句时会提示：“无法截断表 'd'，因为该表正由 FOREIGN KEY 约束引用。”
我们可以这样设想：
1、先找出没有外键约束的表，truncate
２、有外键的表，先delete,再复位identity列
于是得出，
语句丁（注意没有使用游标 ）
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1. SET NoCount ON
2. DECLARE @tableName varchar(512)
3. Declare @SQL varchar(2048)
4. SET @tableName=''
5. WHILE EXISTS
6. (
7. --Find all child tables and those which have no relations
8. SELECT T.table_name FROM INFORMATION_SCHEMA.TABLES T
9. LEFT OUTER JOIN INFORMATION_SCHEMA.TABLE_CONSTRAINTS TC ON T.table_name = TC.table_name
10. WHERE ( TC.constraint_Type = 'Foreign Key' OR TC.constraint_Type IS NULL )
11. AND T.table_name NOT IN ( 'dtproperties', 'sysconstraints', 'syssegments' )
12. AND Table_type = 'BASE TABLE'
13. AND T.table_name > @TableName
14. )
15. Begin
16. SELECT @tableName = min(T.table_name) FROM INFORMATION_SCHEMA.TABLES T
17. LEFT OUTER JOIN INFORMATION_SCHEMA.TABLE_CONSTRAINTS TC ON T.table_name=TC.table_name
18. WHERE ( TC.constraint_Type = 'Foreign Key' OR TC.constraint_Type IS NULL )
19. AND T.table_name NOT IN ( 'dtproperties', 'sysconstraints', 'syssegments' )
20. AND Table_type = 'BASE TABLE'
21. AND T.table_name > @TableName
22. --Truncate the table
23. SET @SQL = 'Truncate table '+ @TableName
24. print (@SQL)
25. Exec(@SQL)
26. End
27.
28. SET @TableName=''
29. WHILE EXISTS
30. (
31. --Find all Parent tables
32. SELECT T.table_name FROM INFORMATION_SCHEMA.TABLES T
33. LEFT OUTER JOIN INFORMATION_SCHEMA.TABLE_CONSTRAINTS TC ON T.table_name = TC.table_name
34. WHERE TC.constraint_Type = 'Primary Key'
35. AND T.table_name <> 'dtproperties'
36. AND Table_type='BASE TABLE'
37. AND T.table_name > @TableName
38. )
39. Begin
40. SELECT @tableName = min(T.table_name) FROM INFORMATION_SCHEMA.TABLES T
41. LEFT OUTER JOIN INFORMATION_SCHEMA.TABLE_CONSTRAINTS TC ON T.table_name=TC.table_name
42. WHERE TC.constraint_Type = 'Primary Key'
43. AND T.table_name <> 'dtproperties'
44. AND Table_type = 'BASE TABLE'
45. AND T.table_name > @TableName
46. --Delete the table
47.
48. SET @SQL = ' delete from '+ @TableName
49. print (@SQL)
50. Exec(@SQL)
51. --Reset identity column
52. IF EXISTS ( SELECT * FROM INFORMATION_SCHEMA.COLUMNS
53. WHERE COLUMNPROPERTY(
54. OBJECT_ID( QUOTENAME(table_schema)+ '.' + QUOTENAME(@tableName) ),
55. column_name,'IsIdentity'
56. ) = 1
57. )
58. DBCC CHECKIDENT(@tableName,RESEED,0)
59. End
60. SET NoCount OFF
SET NoCount ON DECLARE @tableName varchar(512) Declare @SQL varchar(2048) SET @tableName='' WHILE EXISTS ( --Find all child tables and those which have no relations SELECT T.table_name FROM INFORMATION_SCHEMA.TABLES T LEFT OUTER JOIN INFORMATION_SCHEMA.TABLE_CONSTRAINTS TC ON T.table_name = TC.table_name WHERE ( TC.constraint_Type = 'Foreign Key' OR TC.constraint_Type IS NULL ) AND T.table_name NOT IN ( 'dtproperties', 'sysconstraints', 'syssegments' ) AND Table_type = 'BASE TABLE' AND T.table_name > @TableName ) Begin SELECT @tableName = min(T.table_name) FROM INFORMATION_SCHEMA.TABLES T LEFT OUTER JOIN INFORMATION_SCHEMA.TABLE_CONSTRAINTS TC ON T.table_name=TC.table_name WHERE ( TC.constraint_Type = 'Foreign Key' OR TC.constraint_Type IS NULL ) AND T.table_name NOT IN ( 'dtproperties', 'sysconstraints', 'syssegments' ) AND Table_type = 'BASE TABLE' AND T.table_name > @TableName --Truncate the table SET @SQL = 'Truncate table '+ @TableName print (@SQL) Exec(@SQL) End SET @TableName='' WHILE EXISTS ( --Find all Parent tables SELECT T.table_name FROM INFORMATION_SCHEMA.TABLES T LEFT OUTER JOIN INFORMATION_SCHEMA.TABLE_CONSTRAINTS TC ON T.table_name = TC.table_name WHERE TC.constraint_Type = 'Primary Key' AND T.table_name <> 'dtproperties' AND Table_type='BASE TABLE' AND T.table_name > @TableName ) Begin SELECT @tableName = min(T.table_name) FROM INFORMATION_SCHEMA.TABLES T LEFT OUTER JOIN INFORMATION_SCHEMA.TABLE_CONSTRAINTS TC ON T.table_name=TC.table_name WHERE TC.constraint_Type = 'Primary Key' AND T.table_name <> 'dtproperties' AND Table_type = 'BASE TABLE' AND T.table_name > @TableName --Delete the table SET @SQL = ' delete from '+ @TableName print (@SQL) Exec(@SQL) --Reset identity column IF EXISTS ( SELECT * FROM INFORMATION_SCHEMA.COLUMNS WHERE COLUMNPROPERTY( OBJECT_ID( QUOTENAME(table_schema)+ '.' + QUOTENAME(@tableName) ), column_name,'IsIdentity' ) = 1 ) DBCC CHECKIDENT(@tableName,RESEED,0) End SET NoCount OFF
小结：除了以上方法，还可以临时禁用外键约束。语句为：
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1. -- --禁用所有约束
2. --exec sp_msforeachtable 'alter table ? nocheck CONSTRAINT all'
3. -- --再启用所有外键约束
4. --exec sp_msforeachtable 'alter table ? check constraint all'