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SQL and Relational Theory by C. J. Date

Author:C. J. Date [C. J. Date] , Date: August 18, 2015 ,Views: 416

SQL and Relational Theory by C. J. Date

Author:C. J. Date [C. J. Date]
Language: eng
Format: epub, pdf
Tags: COMPUTERS / Data Modeling & Design
ISBN: 9781449316396
Publisher: O'Reilly Media
Published: 2011-12-18T16:00:00+00:00


DFGP: On day DAY, flight FLIGHT with pilot PILOT leaves from gate GATE.

They’re subject to the following constraints (expressed here in a kind of pseudo logical style):

IF ( f1,n1,h ) , ( f2,n2,h ) ∈ FDH AND ( d,f1,g,p1 ) , ( d,f2,g,p2 ) ∈ DFGP THEN f1 = f2 AND p1 = p2 /* and n1 = n2, incidentally */ IF ( f1,n1,h ) , ( f2,n2,h ) ∈ FDH AND ( d,f1,g1,p ) , ( d,f2,g2,p ) ∈ DFGP THEN f1 = f2 AND g1 = g2 /* and n1 = n2, incidentally */

Explanation: The first of these constraints says:

If two rows of FDH, one for flight f1 (with destination n1) and one for flight f2 (with destination n2), have the same HOUR h, and



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