清空mysql指定库里所有表数据

由于项目需要将之前那些测试数据全部清空，几经询问，终于问到一个答案出来，原来可以对mysql中的information_schema这个库里进行操作的。具体可执行： 

 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！