How show up the calculation from other table?

Question

i have a database and 2 tables
this is my code
<?php
$query=mysql_query("select *from cat where k1 like '$k1' and k2 like '$k2'");
while ($row=mysql_fetch_array($query))
$k1 = $row['k1'];
$k2 = $row['k2'];

?>
$k1 have a content and the calculation content $k1 in different table
how can i show up the calculation from other table?

Answer 1

https://www.sololearn.com/learn/SQL/1866/

Answer 2

You can use joins, refer mysql course's joins chapter.