Article View: comp.lang.pascal.delphi.databases
Article #53Outer Joins in BDE - maybe a bug
From: Dominik L�bbers
Date: Wed, 03 Feb 1999 00:00
Date: Wed, 03 Feb 1999 00:00
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Using SQL-Language of the BDE the following problems occured: Guess, we have 3 tables: 1) "Teachers" with a fields ID and a name 2) "Courses" with a field ID, a name and a Teacher-ID 3) "Students" with a field ID, a name and a Course-ID For example these tables content the following data: Teachers ======== ID Name 99 Smith Courses ======= ID Name Teacher 1 Course 1 Students ======== ID Name Course 900 Bart Simpson 1 Notice, that no Teacher-ID is given in the Courses-Table. In this situation the following SQL-Queries give a different result: SELECT * FROM (Courses C INNER JOIN Students S ON S.Course=C.ID) LEFT OUTER JOIN Teachers T ON C.Teacher=T.ID SELECT * FROM (Courses C LEFT OUTER JOIN Teachers T ON C.Teacher=T.ID) INNER JOIN Students S ON S.Course=C.ID In the second case a sentence is given back, in the first case not. Should'nt this be the same? And if not, why not? Hoping, someone find the difference and tells me what to do. Thanks Dominik Luebbers
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X-Google-Language: ENGLISH,ASCII-7-bit X-Google-Thread: ffff5,c6957c4b0ebde685,start X-Google-Attributes: gidffff5,public X-Google-Thread: ff75c,c6957c4b0ebde685,start X-Google-Attributes: gidff75c,public X-Google-Thread: f6386,c6957c4b0ebde685,start X-Google-Attributes: gidf6386,public X-Google-Thread: 10de66,c6957c4b0ebde685,start X-Google-Attributes: gid10de66,public From: "Dominik L�bbers" <dominik@pool.informatik.rwth-aachen.de> Subject: Outer Joins in BDE - maybe a bug Date: 1999/02/03 Message-ID: <36B82492.740C6886@pool.informatik.rwth-aachen.de> X-Deja-AN: 440131102 Content-Transfer-Encoding: 7bit Organization: Aachen University of Technology / Rechnerbetrieb Informatik Content-Type: text/plain; charset=us-ascii Mime-Version: 1.0 Newsgroups: comp.lang.pascal.delphi.databases,borland.public.delphi.database.desktop,borland.public.delphi.database.sqlservers,borland.public.delphi.database.multi-tier