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SQL: Distinct, Group By, or Exists?
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04/06/2003 17:44:38
 
 
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Forum:
Visual FoxPro
Catégorie:
Base de données, Tables, Vues, Index et syntaxe SQL
Titre:
SQL: Distinct, Group By, or Exists?
Divers
Thread ID:
00796420
Message ID:
00796420
Vues:
46
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?
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