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MS Access Forum / New Users / August 20042 Primary Keys
Hi! Can someone explain to me what is the purpose of using more the one primary key in a table? What will be the result of doing so? If I have a table of Products which has two primary keys: 1. ProductID 2. SupplierID If I set the ProductID to be indexed (allow duplicates) and the SupplierID to be indexed (duplicates are not allowed) does that mean I could have different products with the same ID, but not if they are from the same supplier? What is the advantage of using this method of double primary key as opposed to using validation rules? Regards. Just a semantic pont, but, by definition, you can't have 2 primary keys. Are you asking about having a primary key that has more than one field in it? In that case, then yes, you can have the same product for multiple suppliers, but you can't repeat a product for the the same supplier.  SignatureDoug Steele, Microsoft Access MVP http://I.Am/DougSteele (no e-mails, please!) > Hi! > [quoted text clipped - 15 lines] > > Regards. Hi following from Doug's post ... leave the index settings alone ... creating a primary key with two fields will do the type of "validation" that you want .. . however be careful if you set the primary key with the fields described you are in fact saying that supplier A can only EVER buy product A once ... maybe you need to include a date field in the primary key so that supplier A can only purchase product A on a single date, but can purchase product A again later on. Regards JulieD > Just a semantic pont, but, by definition, you can't have 2 primary keys. > [quoted text clipped - 21 lines] > > > > Regards. Hi there! In my DB there is a table with double field primary key: It's primary key is builded from the ReceiptNumber and the ReceiptSupplier Fields. I thought this is good because one supplier can't have more than one Receipt with the same number, but different suppliers can use the same receipt number. What should I put in the index? After all, I want to allow duplicates in the receipt numbers but I only want to allow it if it's for different suppliers. Amir. > Hi > [quoted text clipped - 36 lines] > > > > > > Regards. As Julie said, you put both fields in the primary key. When you have the table open in Design mode, highlight both fields, then click on the "Key" icon to create the primary key. SignatureDoug Steele, Microsoft Access MVP http://I.Am/DougSteele (no e-mails, please!) > Hi there! > [quoted text clipped - 53 lines] > > > > > > > > Regards. OK, Thank you very much! > As Julie said, you put both fields in the primary key. > [quoted text clipped - 61 lines] > > > > > > > > > > Regards. |
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