select * from REFERENTIAL_CONSTRAINTS

来查看这个系统表里的字段及数据。

代码如下：

select CONCAT( 'alter table ', table_name,' drop foreign key ', constraint_name,';') as mystr from REFERENTIAL_CONSTRAINTS where unique_constraint_schema= 'sams4' and table_name in (

select table_name from REFERENTIAL_CONSTRAINTS where unique_constraint_schema= 'sams4'

);

select CONCAT( 'truncate table ', table_name,';') as mystr from REFERENTIAL_CONSTRAINTS where unique_constraint_schema= 'sams4' and table_name in (

select table_name from REFERENTIAL_CONSTRAINTS where unique_constraint_schema= 'sams4'

);

select CONCAT( 'alter table ', table_name,' drop foreign key ', constraint_name,';') as mystr from REFERENTIAL_CONSTRAINTS where unique_constraint_schema= 'sams4' and table_name in (

select table_name from REFERENTIAL_CONSTRAINTS where unique_constraint_schema= 'sams4' nd table_name like 't_%'

);

select CONCAT( 'truncate table ', table_name,';') as mystr from REFERENTIAL_CONSTRAINTS where unique_constraint_schema= 'sams4' and table_name in (

select table_name from REFERENTIAL_CONSTRAINTS where unique_constraint_schema= 'sams4' and table_name like 't_%'

);

其中sams4是我指定的库！以上代码只是一个查出全部表，一个查出所有以t_开头的表名，都是先将表与表之间的外键关联删除后再进行清空表，清空表时用的是truncate table,并不是用delete from table的语句是因为用truncate这个命令里，可以将ID值重置为1.

但这里还有一个问题，就是外键关联的问题，如果要清空表数据的话，一个一个的按顺序来清空，工作量也太大了，如果有办法可以先暂时将这个外键屏蔽的话就好了，所以上网google一下，得出如下：

SET FOREIGN_KEY_CHECKS = 0; #取消外键关联

【执行操作，操作结束后】

SET FOREIGN_KEY_CHECKS = 1; #开启外键关联

至此应该可以有效率地将库里的指定表数据清空！

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2011-11-23 22:04

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分类:数据库

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