Compare two columns from different Table

[Motifaithed]

Hi Guys,

What is the way to compare two columns from different table?Say I want to compare column IDNumber from table 1 to column IDNumber to table 2, after that I want to delete Identical IdNumber and show the remaining unique IDNumber, any idea how to start it?

[suhnako]

maybe it goes like this...

$sql = "SELECT * FROM table1 a
LEFT JOIN table2 b
ON a.IDNumber = b.IDNumber";
$qry = mysql_query($sql);

OK let's assume that you want to delete all duplicates in table2

DELETE FROM table2 WHERE id IN (SELECT id FROM table1)

[Motifaithed]

Thank You very much ardav and suhnako, I'll try your suggestion and update you for the result.

Good Day