Pair problem ( SQL of the query )

Question

Hi,
Do you know how should look an SQL query to make possible viewing pairs, but the pairs cannot repeat ?
For example in emp relation we want to get workers which works in proper department ( table dept) and view it by pairs - but the same pairs cannot repeat e.g.
JONES RESEARCH SMITH
WARD SALES ALLEN
This example result of this query. I have two relations emp and one relation dept and I don't want to get the same names but with the different order -
JONES RESEARCH SMITH
WARD SALES ALLEN
SMITH RESEARCH JONES
ALLEN SALES WARD
this last two shouldn't appear.
Thanks for answer.

Answer 1

If we have got system built-in tables EMP i DEPT with structure
CREATE TABLE EMP
(EMPNO NUMERIC(4) NOT NULL,
ENAME VARCHAR(10),
JOB VARCHAR(9),
MGR NUMERIC(4),
HIREDATE DATETIME,
SAL NUMERIC(7, 2),
COMM NUMERIC(7, 2),
DEPTNO NUMERIC(2))
INSERT INTO EMP VALUES
(7369, ‘SMITH’, ‘CLERK’, 7902, ‘17-DEC-1980′, 800, NULL, 20)
INSERT INTO EMP VALUES
(7499, ‘ALLEN’, ‘SALESMAN’, 7698, ‘20-FEB-1981′, 1600, 300, 30)
INSERT INTO EMP VALUES
(7521, ‘WARD’, ‘SALESMAN’, 7698, ‘22-FEB-1981′, 1250, 500, 30)
INSERT INTO EMP VALUES
(7566, ‘JONES’, ‘MANAGER’, 7839, ‘2-APR-1981′, 2975, NULL, 20)
INSERT INTO EMP VALUES
(7654, ‘MARTIN’, ‘SALESMAN’, 7698, ‘28-SEP-1981′, 1250, 1400, 30)
INSERT INTO EMP VALUES
(7698, ‘BLAKE’, ‘MANAGER’, 7839, ‘1-MAY-1981′, 2850, NULL, 30)
INSERT INTO EMP VALUES
(7782, ‘CLARK’, ‘MANAGER’, 7839, ‘9-JUN-1981′, 2450, NULL, 10)
INSERT INTO EMP VALUES
(7788, ‘SCOTT’, ‘ANALYST’, 7566, ‘09-DEC-1982′, 3000, NULL, 20)
INSERT INTO EMP VALUES
(7839, ‘KING’, ‘PRESIDENT’, NULL, ‘17-NOV-1981′, 5000, NULL, 10)
INSERT INTO EMP VALUES
(7844, ‘TURNER’, ‘SALESMAN’, 7698, ‘8-SEP-1981′, 1500, 0, 30)
INSERT INTO EMP VALUES
(7876, ‘ADAMS’, ‘CLERK’, 7788, ‘12-JAN-1983′, 1100, NULL, 20)
INSERT INTO EMP VALUES
(7900, ‘JAMES’, ‘CLERK’, 7698, ‘3-DEC-1981′, 950, NULL, 30)
INSERT INTO EMP VALUES
(7902, ‘FORD’, ‘ANALYST’, 7566, ‘3-DEC-1981′, 3000, NULL, 20)
INSERT INTO EMP VALUES
(7934, ‘MILLER’, ‘CLERK’, 7782, ‘23-JAN-1982′, 1300, NULL, 10)
CREATE TABLE DEPT
(DEPTNO NUMERIC(2),
DNAME VARCHAR(14),
LOC VARCHAR(13) )
INSERT INTO DEPT VALUES (10, ‘ACCOUNTING’, ‘NEW YORK’)
INSERT INTO DEPT VALUES (20, ‘RESEARCH’, ‘DALLAS’)
INSERT INTO DEPT VALUES (30, ‘SALES’, ‘CHICAGO’)
INSERT INTO DEPT VALUES (40, ‘OPERATIONS’, ‘BOSTON’)
And the aim is to show all workers by pairs but if I have a pair :
JONES RESEARCH SMITH
the pair in opposite direction shouldn't appear ( pair SMITH RESEARCH JONES shouldn't appera), and so on for other pairs.
Thanks for answer.