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table relationships
I have managed to relate two tables but I am having trouble relating my other
tables. I need help with many to many relations.... I think. |
#2
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table relationships
You fix Many-To-Many joins by adding a third bridging or linking table. For
example an Assembly can have many Parts. Also a Part can be used in many Assemblies. This is a classic M-M relationship and relational databases work best with 1-M relationships. This third bridging or linking table has foreign key fields for something like the PartNo from the Parts table primary key and AssemblyID which matches the Assembly table primary key. This combination could be the primary key for the table or at least a unique index to prevent duplicates. You could also have a field for PartCount as an Assembly could use dozens of the same screws for example. With this bridging or linking table, you can ask questions in both directions such as “this assembly uses which parts” or “this part is used on which assemblies” by joining the three tables together in a query -- Jerry Whittle, Microsoft Access MVP Light. Strong. Cheap. Pick two. Keith Bontrager - Bicycle Builder. "Lori" wrote: I have managed to relate two tables but I am having trouble relating my other tables. I need help with many to many relations.... I think. |
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