Information générale
Catégorie:
Base de données, Tables, Vues, Index et syntaxe SQL
Titre:
SQL: Distinct, Group By, or Exists?
Not having strong experience with SQL, I need a little help to get the right result set for a new view.
TableA: PrimaryKey(I), DataItem(C 20)
1, Apples
2, Oranges
3, Pears
4, Bananas
TableB: ForeignKey(I), Condition(L)
1, .T.
1, .T.
2, .F.
4, .T.
4, .T.
4, .F.
Result: PrimaryKey(I), DataItem(C 20)
1, Apples
4, Bananas
(One result from Table A only if there's a True Condition in table B.)
Normally, I'd try to join the tables and use DISTINCT PrimaryKey, or GROUP BY PrimaryKey. Shouldn't those give the same result? Which is better? Does VFP8's change to GROUP BY syntax change this? Would an EXISTS clause (which I've never used before) work?
Suivant
Répondre
Voir le fil de ce thread
Voir le fil de ce thread à partir de ce message seulement
Voir tous les messages de ce thread
Voir tous les messages de ce thread à partir de ce message seulement