Outer Joins in BDE - maybe a bug 
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 Outer Joins in BDE - maybe a bug

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



Wed, 18 Jun 1902 08:00:00 GMT  
 
 [ 1 post ] 

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