Divided Operator

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Divided Operator

ms65g

SSC Rookie

Points: 42
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July 24, 2009 at 4:16 am

#385050

How do we implement DIVIDE OPERATOR in SQL?

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stopitallready SSC Eights! Points: 800 More actions · Answer 1

What are you trying to do? More information is neccessary.

Eli

Jack Corbett SSC Guru Points: 184394 More actions · Answer 2

If you meant the math division operator then you use "/".

Jack Corbett
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ms65g SSC Rookie Points: 42 More actions · Answer 3

stopitallready (7/24/2009)
What are you trying to do? More information is neccessary.
Eli

I mean 8th operator. A divided by B per C

and A,B and C are result set.

A divided by B per C = A minus ( (A times B) minus C)

Lowell SSC Guru Points: 323518 More actions · Answer 4

still not clear to me either, can you give a non-pseudo code, concrete example of the expected results?

Lowell

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David Webb-CDS SSCoach Points: 17398 More actions · Answer 5

If you're talking about the relational division operator, a decent explanation with some SQL as an example is http://www.dbazine.com/ofinterest/oi-articles/celko1.

I'm not a big Celko fan, but this (and the included references) should get you started.

And then again, I might be wrong ...
David Webb

sqlvogel SSCrazy Eights Points: 9526 More actions · Answer 6

Take a look at Vadim Tropashko's book SQL Design Patterns for examples of relational division problems and solutions.

Full marks for a good question by the way. It's a bit unfortunate that Relational Algebra and other relational theory ideas aren't as well appreciated and used in the SQL community as they perhaps ought to be. These concepts give you the tools and a vocabulary for solving lots of every day problems.

Unfortunately, as has often been noted, too many database practitioners today don't know the relational model at all. They just know SQL and someone once told them SQL was relational so they assume they must know the relational stuff too.

Not knocking anyone here BTW. Just my thoughts for this "Relational Theory" forum.

Hope this helps.

ms65g SSC Rookie Points: 42 More actions · Answer 7

Thank you.

I agree with you. a lot of difficult problem solve by using relational algebra.

Dr. CJ Date offered two methods but I was looking for the best solution for division operator.

here is a method: Please exec following script before exec this query

-- My Method

SELECT DISTINCT pilot

FROM PilotSkills AS PS

WHERE NOT EXISTS (

SELECT plane FROM Hangar

EXCEPT

SELECT plane FROM PilotSkills

WHERE PS.pilot=pilot

)

/*

CREATE TABLE PilotSkills

(pilot CHAR(15) NOT NULL,

plane CHAR(15) NOT NULL,

PRIMARY KEY (pilot, plane));

INSERT INTO PilotSkills

SELECT pilot='Celko', plane='Piper Cub'

UNION

SELECT 'Higgins','B-52 Bomber'

UNION

SELECT 'Higgins','F-14 Fighter'

UNION

SELECT 'Higgins','Piper Cub'

UNION

SELECT 'Jones','B-52 Bomber'

UNION

SELECT 'Jones','F-14 Fighter'

UNION

SELECT 'Smith','B-1 Bomber'

UNION

SELECT 'Smith','B-52 Bomber'

UNION

SELECT 'Smith','F-14 Fighter'

UNION

SELECT 'Wilson','B-1 Bomber'

UNION

SELECT 'Wilson','B-52 Bomber'

UNION

SELECT 'Wilson','F-14 Fighter'

UNION

SELECT 'Wilson','F-17 Fighter'

CREATE TABLE Hangar

(plane CHAR(15) NOT NULL PRIMARY KEY);

INSERT INTO Hangar

SELECT plane='B-1 Bomber'

UNION

SELECT 'B-52 Bomber'

UNION

SELECT 'F-14 Fighter'

*/