Hi,
At Wed, 3 Sep 2014 10:38:13 -0700 (PDT), ruby user wrote:
> When i run this query to get Images with tags that are named both
> bamboo in and Green i get an error that says the alias table is not
> present. What am I doing wrong?
>
> Image.joins(:tags).select("images.*, count(tags.id) as
> 'tags_count'").where(tags:{name:["bamboo","Green"]}).group("images.id").having
> ("tags_count = 2")
>
> Error
>
> Image Load (0.4ms) SELECT images.*, count(tags.id) as tags_count FROM
> "images" INNER JOIN "image_tags" ON "image_tags"."image_id" =
> "images"."id" INNER JOIN "tags" ON "tags"."id" = "image_tags"."tag_id" WHERE
> "tags"."name" IN ('bamboo', 'Green') GROUP BY images.id HAVING
> tags_count = 2
>
> PG::UndefinedColumn: ERROR: column "tags_count" does not exist
>
> LINE 1: ... IN ('bamboo', 'Green') GROUP BY images.id HAVING tags_count...
>
> ^Well, "doing it wrong" is not the phrase I would choose. In PostgreSQL, aliases are in a different scope than HAVING. HAVING may not access aliases, you have to repeat the aggregate (will be optimized to not be executed again). This is part of the SQL standard, AFAIK. Best regards, -- Christian Kruse http://ck.kennt-wayne.de/
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