Select from one table where not in another

Question

I\'m trying to find the rows that are in one table but not another, both tables are in different databases and also have different column names on the column that I\'m using

Answer 1

So there's loads of posts on the web that show how to do this, I've found 3 ways, same as pointed out by Johan & Sjoerd. I couldn't get any of these queries to work, well obviously they work fine it's my database that's not working correctly and those queries all ran slow.

So I worked out another way that someone else may find useful:

The basic jist of it is to create a temporary table and fill it with all the information, then remove all the rows that ARE in the other table.

So I did these 3 queries, and it ran quickly (in a couple moments).

CREATE TEMPORARY TABLE

`database1`.`newRows`

SELECT

`t1`.`id` AS `columnID`

FROM

`database2`.`table` AS `t1`

.

CREATE INDEX `columnID` ON `database1`.`newRows`(`columnID`)

.

DELETE FROM `database1`.`newRows`

WHERE

EXISTS(
    SELECT `columnID` FROM `database1`.`product_details` WHERE `columnID`=`database1`.`newRows`.`columnID`
)