SELECT statements with one or more NOT EXISTS clauses - sql

Question

Table LPTitle:
CREATE TABLE LPTitle(
title VARCHAR(30) NOT NULL, /* Position title */
CONSTRAINT LPTitle_pkey PRIMARY KEY ( title ) );
INSERT INTO LPTitle VALUES( 'ASSISTANT' );
INSERT INTO LPTitle VALUES( 'ASSOC. LECTURER' );
INSERT INTO LPTitle VALUES( 'LECTURER' );
INSERT INTO LPTitle VALUES( 'SENIOR LECTURER' );
INSERT INTO LPTitle VALUES( 'ASSOC. PROFESSOR' );
INSERT INTO LPTitle VALUES( 'PROFESSOR' );
Table Position:
CREATE TABLE Position(
p# NUMBER(8) NOT NULL, /* Position number */
ptitle VARCHAR(30) NOT NULL, /* Position title */
employer VARCHAR(100) NOT NULL, /* Institution name */
salary NUMBER(9,2) NOT NULL, /* Salary */
extras VARCHAR(50) , /* Extras */
specification LONG , /* Specification */
CONSTRAINT Position_pkey PRIMARY KEY ( p# ),
CONSTRAINT Position_fkey1 FOREIGN KEY ( ptitle )
REFERENCES LPTitle ( title ) );
INSERT INTO Position VALUES ( 00000001, 'LECTURER', 'UNSW', 45000.00, 'computer', 'Teaching');
INSERT INTO Position VALUES ( 00000002, 'LECTURER', 'UOW', 450000.00, 'mouse pad', 'Research');
INSERT INTO Position VALUES ( 00000003, 'SENIOR LECTURER', 'UTS', 50000.00, NULL, 'A lot of hard work' );
INSERT INTO Position VALUES ( 00000004, 'ASSOC. PROFESSOR', 'UOW', 60000.00, NULL, NULL);
INSERT INTO Position VALUES ( 00000005, 'PROFESSOR', 'UQ', 80000.00, 'chair', 'Research' );
INSERT INTO Position VALUES ( 00000006, 'PROFESSOR', 'UNSW', 80000.00, 'chair', 'Research' );
INSERT INTO Position VALUES ( 00000007, 'PROFESSOR', 'UOW', 80000.00, 'chair', 'Teaching and research');
Table Applies:
CREATE TABLE Applies(
a# NUMBER(6) NOT NULL, /* Applicant number */
p# NUMBER(8) NOT NULL, /* Position number */
appdate DATE NOT NULL, /* Application date */
CONSTRAINT Applies_pkey PRIMARY KEY ( a#, p# ),
CONSTRAINT Applies_fkey1 FOREIGN KEY ( a# )
REFERENCES Applicant ( a# )
ON DELETE CASCADE,
CONSTRAINT Applies_fkey2 FOREIGN KEY ( p# )
REFERENCES Position ( p# )
ON DELETE CASCADE);
INSERT INTO Applies VALUES( 000001, 00000001, TO_DATE('13-DEC-1999','DD-MON-YYYY') );
INSERT INTO Applies VALUES( 000002, 00000001, TO_DATE('13-DEC-1999','DD-MON-YYYY') );
INSERT INTO Applies VALUES( 000003, 00000002, TO_DATE('14-NOV-1999','DD-MON-YYYY') );
INSERT INTO Applies VALUES( 000004, 00000002, TO_DATE('20-JAN-2000','DD-MON-YYYY') );
INSERT INTO Applies VALUES( 000005, 00000002, TO_DATE('22-JAN-2000','DD-MON-YYYY') );
INSERT INTO Applies VALUES( 000005, 00000003, TO_DATE('09-MAY-1999','DD-MON-YYYY') );
INSERT INTO Applies VALUES( 000006, 00000003, TO_DATE('17-JUN-1999','DD-MON-YYYY') );
INSERT INTO Applies VALUES( 000007, 00000003, TO_DATE('18-JUN-1999','DD-MON-YYYY') );
INSERT INTO Applies VALUES( 000007, 00000004, TO_DATE('13-APR-2000','DD-MON-YYYY') );
INSERT INTO Applies VALUES( 000008, 00000004, TO_DATE('13-APR-2000','DD-MON-YYYY') );
INSERT INTO Applies VALUES( 000009, 00000004, TO_DATE('14-APR-2000','DD-MON-YYYY') );
INSERT INTO Applies VALUES( 000010, 00000005, TO_DATE('23-SEP-1999','DD-MON-YYYY') );
INSERT INTO Applies VALUES( 000001, 00000006, TO_DATE('26-OCT-1999','DD-MON-YYYY') );
INSERT INTO Applies VALUES( 000002, 00000006, TO_DATE('27-OCT-1999','DD-MON-YYYY') );
INSERT INTO Applies VALUES( 000003, 00000006, TO_DATE('28-OCT-1999','DD-MON-YYYY') );
INSERT INTO Applies VALUES( 000004, 00000007, TO_DATE('01-JAN-2000','DD-MON-YYYY') );
INSERT INTO Applies VALUES( 000005, 00000007, TO_DATE('03-JAN-2000','DD-MON-YYYY') );
INSERT INTO Applies VALUES( 000006, 00000007, TO_DATE('04-JAN-2000','DD-MON-YYYY') );
INSERT INTO Applies VALUES( 000007, 00000007, TO_DATE('07-JAN-2000','DD-MON-YYYY') );
With the 3 tables above, I want to find the titles of all positions that have no applications. How to implements this by using SELECT statements with one or more NOT EXISTS clauses?
This is the query I have so far, the result is always "no rows selected" (which is wrong):
SELECT
LPTitle.title
FROM
LPTitle
FULL OUTER JOIN
Position
ON
LPTitle.title = Position.ptitle
WHERE
NOT EXISTS
(
SELECT Applies.p# FROM Applies INNER JOIN Position ON Applies.p# = Position.p#
)
;

Answer 1

I think the query below will do the job. Please note that you don't need the LPTitle table, as you already have all title values stored in Position tables ptitle column.
Basicly the result is the same: you have an application for all of your 7 positions!
SELECT
p.ptitle
FROM
Position p
WHERE
NOT EXISTS
(
SELECT 1 FROM Applies WHERE p# = p.p#
)
;
If you meant to look for all unused titles, than that's another task:
SELECT
l.title
FROM
LPTitle l
WHERE
NOT EXISTS
(
SELECT 1 FROM Position ptitle = l.title
)
;