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@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          torturing
2          accounts

(The torturing department has two employees)

TIA
cw Received on Sun May 16 2004 - 16:05:15 CDT