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Free tables vs DBC
Message
De
11/01/2003 15:20:52
Hilmar Zonneveld
Independent Consultant
Cochabamba, Bolivie
 
 
À
11/01/2003 15:09:51
Tom Gahagan
Alliance Computer Solutions
Thomaston, Georgie, États-Unis
Information générale
Forum:
Visual FoxPro
Catégorie:
Base de données, Tables, Vues, Index et syntaxe SQL
Divers
Thread ID:
00740632
Message ID:
00740690
Vues:
30
>With a gradeing system you will probably have some many to many relationships...so be aware of the potential problems with this.

In most moderately complex system, you will sooner or later have many-to-many relationships. This is solved by creating an intermediate table, that resolves the many-to-many relationships into two one-to-many relationships.

For instance, in the case of a grading system, you can have a table "subjects" and a table "students". There is a many-to-many relationship between the two - many students take the same subject, and one student takes many subjects. The "intermediate table" could be called "grades", and it has foreign keys to both students and subjects.

Additional explanations at http://www.levelextreme.com/Magazine/August2002/Page7.asp.
Difference in opinions hath cost many millions of lives: for instance, whether flesh be bread, or bread be flesh; whether whistling be a vice or a virtue; whether it be better to kiss a post, or throw it into the fire... (from Gulliver's Travels)
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