Using column alias in WHERE clause of MySQL query produces an error

Question

The query I\'m running is as follows, however I\'m getting this error:

#1054 - Unknown column \'guaranteed_postcode\' in \'IN/ALL/ANY subquery\'

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Answer 1

I am using mysql 5.5.24 and the following code works:

select * from (
SELECT `users`.`first_name`, `users`.`last_name`, `users`.`email`,
SUBSTRING(`locations`.`raw`,-6,4) AS `guaranteed_postcode`
FROM `users` LEFT OUTER JOIN `locations`
ON `users`.`id` = `locations`.`user_id`
) as a
WHERE guaranteed_postcode NOT IN --this is where the fake col is being used
(
 SELECT `postcode` FROM `postcodes` WHERE `region` IN
 (
  'australia'
 )
)