Re: join table problem
От | Oliveiros d'Azevedo Cristina |
---|---|
Тема | Re: join table problem |
Дата | |
Msg-id | 4283335591EA4532BCE90938FCF5136F@marktestcr.marktest.pt обсуждение исходный текст |
Ответ на | join table problem (Jedrin <jrubiando@gmail.com>) |
Список | pgsql-sql |
Howdy! > At any rate, say I have 3 tables: > > table plant > id:integer > name string > > > table seed_supplier > id: integer > company_name: string > > table plant_seed_supplier > plant_id > seed_supplier_id > > plant_seed_supplier is a join table that supports a many to many > relationship between the plant table and the seed supplier table since > any plant may have multiple seed suppliers and any seed supplier can > sell seeds for many different plants. > > I would like to be able to write a single query that basically does > this: > > It will show only one distinct row for each plant in the database. It > will show either just one seed_supplier company name associated with > that plant, or if there is no supplier associated with that plant it > will show the plant in a row with that field empty. > You do not specify what is the seed_supplier company name that should appear in the case there is more than one Give this (untested) query a try SELECT name,MIN(company_name) FROM plant a JOIN plant_seed_supplier associative ON plant_id = a.id JOIN seed_supplier b ON b.id = supplier_id GROUP BY name Best, Oliveiros
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