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turning attibute values into relations?

From: ruben safir <ruben_at_mrbrklyn.com>
Date: Thu, 11 Dec 2014 11:40:33 -0500
Message-ID: <5489C901.7040301_at_mrbrklyn.com> 





I know that usenet is bad for homework but this problem is driving me crazy



I need some expertise outside my current ring of contacts.



This question is


(e) Retrieve the names of employees who work on every project



Which I think is saying find the employees that work on ALL projects.



How do you turn a relationship into an atribute that can be quried on



This is the relavent relations (tables)


SQL> descr employee

 Name                                      Null?    Type
 ----------------------------------------- --------


----------------------------

 FNAME                                     NOT NULL VARCHAR2(20)
 MINIT                                              CHAR(1)
 LNAME                                     NOT NULL VARCHAR2(20)
 SSN                                       NOT NULL NUMBER(9)
 BDATE                                     NOT NULL DATE
 ADDRESS                                   NOT NULL VARCHAR2(50)
 SEX                                       NOT NULL CHAR(1)
 SALARY                                    NOT NULL FLOAT(12)
 SUPERSSN                                           NUMBER(9)
 DNO
                                        NUMBER(2)


SQL> descr PROJECT
 Name                                      Null?    Type
 ----------------------------------------- --------


----------------------------

 PNAME                                     NOT NULL VARCHAR2(20)
 PNUMBER                                   NOT NULL NUMBER(2)
 PLOCATION                                 NOT NULL VARCHAR2(15)
 DNUM
                                          NUMBER(2)
SQL> descr works_on
 Name                                      Null?    Type
 ----------------------------------------- --------


----------------------------

 ESSN                                      NOT NULL NUMBER(9)
 PNO                                       NOT NULL NUMBER(2)
 HOURS                                              FLOAT(5)







So you want a query that includes off the essn's in workson that
associated with all the possible pno and match pnumbers in projects.



I tried this in SQL and in relational algebra  and I can't see a path to
a solution.



Ruben
Received on Thu Dec 11 2014 - 17:40:33 CET












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