MESSAGE
| DATE | 2014-12-11 |
| FROM | Ruben Safir
|
| SUBJECT | Subject: [NYLXS - HANGOUT] Fwd: turning attibute values into relations?
|
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
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