easy (I think) dbase/FoxPro question (about JOIN)

easy (I think) dbase/FoxPro question (about JOIN)

Post by David P. Caldwe » Wed, 11 Oct 1995 04:00:00



        OK.  I have two databases.  They are linked by a one-to-many
mapping.  That is, Database A has a primary key.  For each entry in
Database A, there are 0, 1, or many entries in Database B which share the
primary key.

        If I join the two databases, I get Database B.  (There are no *
entries in Database B which do not join to A).  On the other hand, there
are many entries in Database A with no corresponding entries in Database B.

        How can I generate a list of all entries in Database A with NO
corresponding entries in Database B?

        I hope this question sounds clearer to you than it does to me.  My
apologies for my lack of facility with database terms.

        Replies by E-mail, please, as I expect the answer to this to be
trivial.

-- David.

 
 
 

1. Newbie - Easy (I think) SQL Syntax Question, 3 table join

I have three identical tables, t1, t2, t3

Each table contains a complete list of files on a particular server.

One of the fields in each table is owner (the owner of an individual
file)

What is the SQL syntax to get a list of all the files owned by a
single user "abcde" from the three tables ?

I can do this in three statements:

Select * from t1 where t1.owner = "abcde";
Select * from t2 where t2.owner = "abcde";
Select * from t3 where t3.owner = "abcde";

The question is how can I do this in one statement?

Here is my first attempt:

Select * from t1,t2,t3
where t1.owner = "abcde"
and t1.owner = t2.owner
and t2.owner = t3.owner

This fails to give the correct answer.

select * from (t1 INNER JOIN t2 on t1.owner = t2.owner) INNER JOIN t3
on t3.owner = t1.owner

This also fails to give the correct answer.

Thanks,

John

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