Delete Deletes multiple table data, how can you delete data from multiple relational tables at the same time? Here's an in-depth explanation:
1. Delete from T1 where condition
2, delete t1 from T1 where condition
3, delete t1 from T1,t2 where condition
4, delete t1,t2 from t1,t2 where condition
The first 3 are feasible, and the 4th is not.
That is, simple with the DELETE statement cannot do multiple table delete data operations, but you can establish a cascade delete, the two tables to establish a cascade delete relationship, you can implement the data deleted one table, while deleting the related data in another table.
1, from the data table t1 those ID values in the datasheet t2 have matching records are deleted
Delete T1 from t1,t2 where t1.id=t2.id or DELETE from T1 USING t1,t2 where t1.id=t2.id
2, from the datasheet T1 in the data table T2 no matching records to find out and delete
DELETE T1 from T1 left join T2 on t1.id=t2.id WHERE t2.id is NULL or DELETE from t1,using T1 left join T2 on T1.id=t2.id WH ERE T2.id is NULL
3, from the two tables to find the same record of data and two of the data in the table deleted
DELETE t1,t2 from T1 left JOIN T2 on T1.id=t2.id WHERE t1.id=25
Note that the t1,t2 in the delete t1,t2 from here cannot be an alias
such as: Delete T1,T2 from table_name as T1 left join Table2_name as T2 on t1.id=t2.id where table_name.id=25 execution in the data is incorrect (MYSQL edition This is not less than 5.0 in 5.0 is OK)
The above statement is rewritten as
Delete Table_name,table2_name from table_name as T1 left join Table2_name as T2 on T1.id=t2.id where table_name.id=25 in the data Face execution is wrong (MYSQL version is less than 5.0 in 5.0 is OK)
Transfer from (http://llsljh.iteye.com/blog/708064)
