使用MSSQL2005,如果我首先截断子表(具有FK关系的主键的表),我可以截断带有外键约束的表吗?

我知道我也可以

使用不带where子句的DELETE,然后RESEED标识(或) 删除FK,截断表,并重新创建FK。

我认为只要我在父表之前截断子表,我就可以不做上面的任何一个选项,但我得到了这个错误:

不能截断表'TableName',因为它被一个FOREIGN KEY约束引用。


当前回答

下面的工作对我来说,即使有FK约束,并结合以下答案,只删除指定的表:

事务自动回滚 循环使用逗号分隔的列表 执行动态SQL(使用变量中的表名) DELETE和RESEED表(在这个线程中)


USE [YourDB];

DECLARE @TransactionName varchar(20) = 'stopdropandroll';

BEGIN TRAN @TransactionName;
set xact_abort on; /* automatic rollback https://stackoverflow.com/a/1749788/1037948 */
    -- ===== DO WORK // =====

    -- dynamic sql placeholder
    DECLARE @SQL varchar(300);

    -- LOOP: https://stackoverflow.com/a/10031803/1037948
    -- list of things to loop
    DECLARE @delim char = ';';
    DECLARE @foreach varchar(MAX) = 'Table;Names;Separated;By;Delimiter' + @delim + 'AnotherName' + @delim + 'Still Another';
    DECLARE @token varchar(MAX);
    WHILE len(@foreach) > 0
    BEGIN
        -- set current loop token
        SET @token = left(@foreach, charindex(@delim, @foreach+@delim)-1)
        -- ======= DO WORK // ===========

        -- dynamic sql (parentheses are required): https://stackoverflow.com/a/989111/1037948
        SET @SQL = 'DELETE FROM [' + @token + ']; DBCC CHECKIDENT (''' + @token + ''',RESEED, 0);'; -- https://stackoverflow.com/a/11784890
        PRINT @SQL;
        EXEC (@SQL);

        -- ======= // END WORK ===========
        -- continue loop, chopping off token
        SET @foreach = stuff(@foreach, 1, charindex(@delim, @foreach+@delim), '')
    END

    -- ===== // END WORK =====
-- review and commit
SELECT @@TRANCOUNT as TransactionsPerformed, @@ROWCOUNT as LastRowsChanged;
COMMIT TRAN @TransactionName;

注意:

我认为这仍然有助于按照你想要删除的顺序声明表(即先删除依赖项)。从这个答案中可以看出,不是循环特定的名称,而是用所有表替换

EXEC sp_MSForEachTable 'DELETE FROM ?; DBCC CHECKIDENT (''?'',RESEED, 0);';

其他回答

好吧,因为我没有找到我使用的非常简单的解决方案的例子,这是:

删除外键; 截断表 重新创建外键

是这样的:

1)查找导致失败的外键名称(例如:FK_PROBLEM_REASON,带字段ID,来自表TABLE_OWNING_CONSTRAINT) 2)从表中删除该键:

ALTER TABLE TABLE_OWNING_CONSTRAINT DROP CONSTRAINT FK_PROBLEM_REASON

3)截断招聘表

TRUNCATE TABLE TABLE_TO_TRUNCATE

4)重新添加第一个表的键:

ALTER TABLE TABLE_OWNING_CONSTRAINT ADD CONSTRAINT FK_PROBLEM_REASON FOREIGN KEY(ID) REFERENCES TABLE_TO_TRUNCATE (ID)

就是这样。

正确的;你不能截断一个有FK约束的表。

通常我的处理方法是:

去掉约束 截断表格 重新创建约束。

(当然,这一切都在一笔交易中。)

当然,这只适用于子节点已经被截断的情况。否则,我会走不同的路线,完全取决于我的数据是什么样子的。(变量太多,不便在此赘述。)

最初的海报决定了为什么会这样;更多细节请看这个答案。

因为TRUNCATE TABLE是一个DDL命令,所以它不能检查表中的记录是否被子表中的记录引用。

这就是为什么DELETE有效而TRUNCATE TABLE无效的原因:因为数据库能够确保它没有被另一条记录引用。

你可以按照这个步骤来做, 通过重新播种表,可以删除表中的数据。

delete from table_name
dbcc checkident('table_name',reseed,0)

如果出现错误,则必须重新播种主表。

这是我对这个问题的解决方案。我用它来改变PK,但想法是一样的。希望这将是有用的)

PRINT 'Script starts'

DECLARE @foreign_key_name varchar(255)
DECLARE @keycnt int
DECLARE @foreign_table varchar(255)
DECLARE @foreign_column_1 varchar(255)
DECLARE @foreign_column_2 varchar(255)
DECLARE @primary_table varchar(255)
DECLARE @primary_column_1 varchar(255)
DECLARE @primary_column_2 varchar(255)
DECLARE @TablN varchar(255)

-->> Type the primary table name
SET @TablN = ''
---------------------------------------------------------------------------------------    ------------------------------
--Here will be created the temporary table with all reference FKs
---------------------------------------------------------------------------------------------------------------------
PRINT 'Creating the temporary table'
select cast(f.name  as varchar(255)) as foreign_key_name
    , r.keycnt
    , cast(c.name as  varchar(255)) as foreign_table
    , cast(fc.name as varchar(255)) as  foreign_column_1
    , cast(fc2.name as varchar(255)) as foreign_column_2
    , cast(p.name as varchar(255)) as primary_table
    , cast(rc.name as varchar(255))  as primary_column_1
    , cast(rc2.name as varchar(255)) as  primary_column_2
    into #ConTab
    from sysobjects f
    inner join sysobjects c on  f.parent_obj = c.id 
    inner join sysreferences r on f.id =  r.constid
    inner join sysobjects p on r.rkeyid = p.id
    inner  join syscolumns rc on r.rkeyid = rc.id and r.rkey1 = rc.colid
    inner  join syscolumns fc on r.fkeyid = fc.id and r.fkey1 = fc.colid
    left join  syscolumns rc2 on r.rkeyid = rc2.id and r.rkey2 = rc.colid
    left join  syscolumns fc2 on r.fkeyid = fc2.id and r.fkey2 = fc.colid
    where f.type =  'F' and p.name = @TablN
 ORDER BY cast(p.name as varchar(255))
---------------------------------------------------------------------------------------------------------------------
--Cursor, below, will drop all reference FKs
---------------------------------------------------------------------------------------------------------------------
DECLARE @CURSOR CURSOR
/*Fill in cursor*/

PRINT 'Cursor 1 starting. All refernce FK will be droped'

SET @CURSOR  = CURSOR SCROLL
FOR
select foreign_key_name
    , keycnt
    , foreign_table
    , foreign_column_1
    , foreign_column_2
    , primary_table
    , primary_column_1
    , primary_column_2
    from #ConTab

OPEN @CURSOR

FETCH NEXT FROM @CURSOR INTO @foreign_key_name, @keycnt, @foreign_table,         @foreign_column_1, @foreign_column_2, 
                        @primary_table, @primary_column_1, @primary_column_2

WHILE @@FETCH_STATUS = 0
BEGIN

    EXEC ('ALTER TABLE ['+@foreign_table+'] DROP CONSTRAINT ['+@foreign_key_name+']')

FETCH NEXT FROM @CURSOR INTO @foreign_key_name, @keycnt, @foreign_table, @foreign_column_1, @foreign_column_2, 
                         @primary_table, @primary_column_1, @primary_column_2
END
CLOSE @CURSOR
PRINT 'Cursor 1 finished work'
---------------------------------------------------------------------------------------------------------------------
--Here you should provide the chainging script for the primary table
---------------------------------------------------------------------------------------------------------------------

PRINT 'Altering primary table begin'

TRUNCATE TABLE table_name

PRINT 'Altering finished'

---------------------------------------------------------------------------------------------------------------------
--Cursor, below, will add again all reference FKs
--------------------------------------------------------------------------------------------------------------------

PRINT 'Cursor 2 starting. All refernce FK will added'
SET @CURSOR  = CURSOR SCROLL
FOR
select foreign_key_name
    , keycnt
    , foreign_table
    , foreign_column_1
    , foreign_column_2
    , primary_table
    , primary_column_1
    , primary_column_2
    from #ConTab

OPEN @CURSOR

FETCH NEXT FROM @CURSOR INTO @foreign_key_name, @keycnt, @foreign_table, @foreign_column_1, @foreign_column_2, 
                         @primary_table, @primary_column_1, @primary_column_2

WHILE @@FETCH_STATUS = 0
BEGIN

    EXEC ('ALTER TABLE [' +@foreign_table+ '] WITH NOCHECK ADD  CONSTRAINT [' +@foreign_key_name+ '] FOREIGN KEY(['+@foreign_column_1+'])
        REFERENCES [' +@primary_table+'] (['+@primary_column_1+'])')

    EXEC ('ALTER TABLE [' +@foreign_table+ '] CHECK CONSTRAINT [' +@foreign_key_name+']')

FETCH NEXT FROM @CURSOR INTO @foreign_key_name, @keycnt, @foreign_table, @foreign_column_1, @foreign_column_2, 
                         @primary_table, @primary_column_1, @primary_column_2
END
CLOSE @CURSOR
PRINT 'Cursor 2 finished work'
---------------------------------------------------------------------------------------------------------------------
PRINT 'Temporary table droping'
drop table #ConTab
PRINT 'Finish'