从多个表中删除多行

Question

I have this query that works fine. Its deletes records that are old based on current time.

$cleanacc_1 = "DELETE FROM $acc_1 
    WHERE `Scheduled` < DATE_SUB(UTC_TIMESTAMP(), INTERVAL 30 SECOND)";

$result = mysql_query($cleanacc_1);

However, there are over 100 tables (accounts) that need deleting and I was wondering if I can combine them into one query. If possible how?

Answer 1

No way to do that, AFAIK; anyways, I don't think it would be a big problem to run 100 queries, assuming you are not running that for each request or so..

Are you expecting performance issues? If that's the case, I'd probably use a cron job to run that query every X minutes..

Answer 2

You could setup a view of the tables and do then run the delete sql against the view. That should delete the underlying table data as well. Your table schema and permissions could have an affect whether this will work or not. Check out this answer, it might help as well.

Does deleting row from view delete row from base table - MYsql?

Answer 3

This implies you create a new table for every account. Why are you not creating a record for each account within a single table?

For example...

create table account (id int unsigned primary key auto_increment, other fields...);

If you alter your table structure you will be able to delete individual account records with a single query...

delete from account where condition=true;

Individual transaction records for each account are then stored in another table and contain the account id they relate to...

create table transaction (id, account_id, other transaction fields);

If you don't change the database design you'll need to write PHP code that loops through each table and runs your delete query. This is very inefficient and I urge you to redesign the table as suggested.

If you don't understand why my table redsign suggestion is a better approach, post more information about your database and I'll explain in more detail with a working example.

Answer 4

Please consider the following example.

I have three tables in following structure.

Table names : t1,t2,t3

Fields : Id, name

Im going to perform delete query with one condition which recode id must less than 10.

DELETE FROM t1, t2,t3 USING t1 INNER JOIN t2 INNER JOIN t3 WHERE t1.id<10 and t2.id<10 and t3.id<10.

The query has been successfully executed ( MySql ). I got the expected output.

So please try the same way with your condition.