-----Message d'origine-----
De : Freshman [mailto:abc@msn.com]
Envoyé : jeudi 30 octobre 2003 13:38
À : pgsql-sql@postgresql.org
Objet : [SQL] Please help me to slove this SQL statements
There are three table in database which is suppliers, projects, and
shipments
suppliers contain suppliers id, name ...etc
projects contain project name ..suppliers ID ( J1---J7) ...etc
shipments table contain suppliers ID , PROJECTS ID
how can i query to find out the suppliers to supply all the projects ID
I would suggest:
SELECT * from suppliers
WHERE NOT EXISTS(SELECT * FROM projectsWHERE NOT EXISTS( SELECT * from shipments WHERE shipments.suppliers_ID =
suppliers_suppliers_id AND shipments.project_ID = project.project_id)
);
so you select every supplier who didn't miss any project.
Is that you want to do?
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TIP 9: the planner will ignore your desire to choose an index scan if your joining column's datatypes do not match