relational algebra - semi joins
From: code_wrong <tac_at_tac.ouch.co.uk>
Date: Sun, 16 May 2004 22:05:15 +0100
Message-Id: <1084741452.6632.0_at_eunomia.uk.clara.net>
Hi,
consider 2 relations/tables
Employees and Depts (departments)
Each Dept has one or many Employees
Each Employee has one Dept only
Employees has a foreign key into Depts.
Date: Sun, 16 May 2004 22:05:15 +0100
Message-Id: <1084741452.6632.0_at_eunomia.uk.clara.net>
Hi,
consider 2 relations/tables
Employees and Depts (departments)
Each Dept has one or many Employees
Each Employee has one Dept only
Employees has a foreign key into Depts.
Now if we use a right semi-join
the resulting table will be a list of the records
in Depts where there is one or many Employees in the
Employees table.
My questions is this:
If there are more than one employees in a department
does the result of the semi join have duplicate records
???
ie
Dept#, dept_name
1 torturing 1 torturing2 accounts
(The torturing department has two employees)
TIA
cw
Received on Sun May 16 2004 - 23:05:15 CEST