mysql_query sends a unique query (multiple queries are not supported) to the currently active database on the server that's associated with the specified link_identifier.
An SQL query
The query string should not end with a semicolon. Data inside the query should be properly escaped.
The MySQL connection. If the link identifier is not specified, the last link opened by mysql_connect is assumed. If no such link is found, it will try to create one as if mysql_connect had been called with no arguments. If no connection is found or established, an E_WARNING level error is generated.
For SELECT, SHOW, DESCRIBE, EXPLAIN and other statements returning resultset, mysql_query returns a resource on success, or false on error.
For other type of SQL statements, INSERT, UPDATE, DELETE, DROP, etc, mysql_query returns true on success or false on error.
The returned result resource should be passed to mysql_fetch_array, and other functions for dealing with result tables, to access the returned data.
Use mysql_num_rows to find out how many rows were returned for a SELECT statement or mysql_affected_rows to find out how many rows were affected by a DELETE, INSERT, REPLACE, or UPDATE statement.
mysql_query will also fail and return false if the user does not have permission to access the table(s) referenced by the query.