| db design problem [message #225510] |
Tue, 20 March 2007 03:29  |
Moali72
Messages: 2
Registered: March 2007
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Junior Member |
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hi,
i have problem in design db of my system
here what i have:
i have customers with many branches &
each branch has many machines &
each machine exists in many branches
Also : each machine has many components
each component exists in many machines
Also each branch has many machines with it's components , and each component in this branch machine has it's serial Number
now how i draw this as i am confused
thx ,waiting for your apprecaited reply
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| Re: db design problem [message #225644 is a reply to message #225510] |
Tue, 20 March 2007 12:46  |
Frank
Messages: 7901
Registered: March 2000
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Senior Member |
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This depends on whether you are doing a functional design (Entity modelling) or a technical design (Table modelling). In an Entity-Relation Diagram, you can draw an n to m relation between two entities (e.g. machine and component)
In a technical design, you would create an intermediate table between the machines- and components tables. In this you have two columns: the PK-column of the machines table and the PK column of the components table.
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