sql - Do subselects do an implicit join? -

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I have a SQL query that seems to work but why I really do not understand That's why I greatly appreciate if someone is helping someone to explain what is happening:

Question Returns: All organizations who do not have any comments that have not been created by the consultant Who had set up the organization record. Organizations \ "where \" organization \ ". \" Id \ "(select \" comments \ ". \" Commentable_id \ comments \ "where \" comment \ ". \" Commentable_type \ "= 'Organization' and ( comments.author_id! = Organizas.consultant_id) \ "comments \" command \ "made_at \" ASC)

it is worth it.

I understand why the part is not (comments.author_id! = Organization.consultant_id) is working!? I do not understand how the postgres know this too What is the "organization" within that organization? It has not been defined here.

If it was written as a join, where I was involved in the comments in organizations, then I fully understand how you can do something like this. but in this case it is a subgenre. it shows how how comments and where to map the organizations of the table and those outside the (comments.author_id! = Organizasations.consultant_id)

This sub-row is in the line, so it can see all the columns in that row. You may select from this 

  organizations. * To get better performance from such organizations where no one selected observations (where commentable_type = 'organization' and author_id! = Organizations.consultant_id)

Note that commentable_type is not required to qualify because more than any other code outside the sub code is comment priority. And if there is no consultant_id column in comment , it would be possible to exclude its eligibility, although not recommended for better clarity.

Order in your query does not buy anything, only added value.


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