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POSQLAlchemy: select over multiple tables
 

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    <p>I wanted to optimize my database query:</p> <pre><code>link_list = select( columns=[link_table.c.rating, link_table.c.url, link_table.c.donations_in], whereclause=and_( not_(link_table.c.id.in_( select( columns=[request_table.c.recipient], whereclause=request_table.c.donator==donator.id ).as_scalar() )), link_table.c.id!=donator.id, ), limit=20, ).execute().fetchall() </code></pre> <p>and tried to merge those two selects in one query:</p> <pre><code>link_list = select( columns=[link_table.c.rating, link_table.c.url, link_table.c.donations_in], whereclause=and_( link_table.c.active==True, link_table.c.id!=donator.id, request_table.c.donator==donator.id, link_table.c.id!=request_table.c.recipient, ), limit=20, order_by=[link_table.c.rating.desc()] ).execute().fetchall() </code></pre> <p>the database-schema looks like:</p> <pre><code>link_table = Table('links', metadata, Column('id', Integer, primary_key=True, autoincrement=True), Column('url', Unicode(250), index=True, unique=True), Column('registration_date', DateTime), Column('donations_in', Integer), Column('active', Boolean), ) request_table = Table('requests', metadata, Column('id', Integer, primary_key=True, autoincrement=True), Column('recipient', Integer, ForeignKey('links.id')), Column('donator', Integer, ForeignKey('links.id')), Column('date', DateTime), ) </code></pre> <p>There are several links (donator) in request_table pointing to one link in the link_table. I want to have links from link_table, which are not yet "requested".</p> <p>But this does not work. Is it actually possible, what I'm trying to do? If so, how would you do that?</p> <p>Thank you very much in advance!</p>
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    1. COI solved this issue my own. I needed an left outer join, because it is a many-to-one relation. Thanks!
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    2. CO@ahojnnes: Please post your solution in the answers, for history purposes.
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    3. COto be honest my solution was no solution, because in the end I realized that it did something different. But at the moment I reached a point, where I think this is not possible with joins - at least not as efficient as with the two select's. So I would be still glad about an answer!
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