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

JA
James
1 month ago
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Problem Description
The query I'm running is as follows, however I'm getting this error: > \#1054 - Unknown column 'guaranteed_postcode' in 'IN/ALL/ANY subquery' 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` WHERE `guaranteed_postcode` NOT IN #this is where the fake col is being used ( SELECT `postcode` FROM `postcodes` WHERE `region` IN ( 'australia' ) ) My question is: why am I unable to use a fake column in the where clause of the same DB query?

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