Why does combining my SQL queries into one not work?

Question

These two PHP MySQL queries work.

mysql_query("DELETE FROM videos WHERE id='10';");
mysql_query("DELETE FROM comments WHERE videoId='10';");

This single query fails due to a MySQL syntax error pertinent to the latter DELETE operation.

mysql_query("DELETE FROM videos WHERE id='10';DELETE FROM comments WHERE videoId='10';");

I've stared hard and can't see the syntax error. What is it?

similar to that other question, but this one is much more concise — Randy, Mar 03 '12 at 18:38

score 3 · Answer 1 · edited May 23 '17 at 12:12

3

Not supported by mysql_query see How can I put two queries in one mysql_query? use http://docs.php.net/mysqli.multi-query

edited May 23 '17 at 12:12

Community

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answered Mar 03 '12 at 18:35

dotoree

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score 1 · Accepted Answer · answered Mar 03 '12 at 18:35

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You cannot execute multiple queries with mysql_query. If you really want to (security risk!), use mysql_multi_query. (And you should use the newer mysqli_* functions). It's a good idea two embed those two calls in a transaction.

But this looks a lot like you really want to define foreign key constraints. I highly recommend them, if you are already using InnoDB.

answered Mar 03 '12 at 18:35

knittl

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Thanks! Why is it a security risk to run many queries at once? And indeed, I'm trying to enforce foreign key constraints. – dangerChihuahua007 Mar 03 '12 at 18:56
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Security risk, if you use user supplied data in your queries and fail to escape a single value (sql injections). This cannot happen with prepared statements, but I don't think prepared statements allow multiple queries with a single command either. – knittl Mar 03 '12 at 18:57

score 1 · Answer 3 · answered Mar 03 '12 at 18:36

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Multiples queries are not supported in this function.

http://php.net/manual/en/function.mysql-query.php

answered Mar 03 '12 at 18:36

nosbor

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Why does combining my SQL queries into one not work?

3 Answers3