Optimizing MYSQL Join Queries
Using join queries can make it quite convenient to retrieve data from two or more tables. However, when you use an ORDER BY or GROUP BY expression with a join it should make reference to a column from just one able. For example, you may want to order by article id from one table.
The code below shows a query that orders the data from a join based on the id order from table 1..
$command = "SELECT table1.id, table1.firstname, table1.lastname, table2.email FROM tablename1 as table1, tablename2 as table2 WHERE table1.id=table2.client_id ORDER BY table1.id ASC ";