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MS Access Forum / Database Design / February 2008composite key
I have never dealt w/ a composite key before. I have a table with primary keys of itemsku and date. Does this Composite Key guarantee that there will be no duplicates? thanks. Patti A table has only one "primary key". That key can be a composite of more than one field/column. Before we can guarantee no duplicates, you need to tell us more about your [itemsku] and [date] values. Yes, if the two fields together are your primary key, Access will prevent any duplication OF THOSE COMBINED FIELDS. You could still have the same [itemsku] in multiple records, and you could still have the same [date] in multiple records, but only one instance of the unique combination of these. By the way, Access treats the word "date" as a reserved word. You'll never know what Access is going to use (and Access may not understand what you want to use) -- change the name of this field to something more meaningful, and not a reserved word. Regards Jeff Boyce Microsoft Office/Access MVP >I have never dealt w/ a composite key before. I have a table with primary > keys of itemsku and date. Does this Composite Key guarantee that there > will > be no duplicates? > > thanks. thanks jeff. i inherited undocumented databases. benn grappling w/ so many issues. Would love to rebuild them all but time and money disallow. I do appreciate your pointing out such things as reserved words (that i do know about). I am always looking to learn, so anytime a flaw is explained, i perk up. In the table design, i saw the litlle key symbol next to itemsku and date fields, hence my error in referring to primary keys. Those 2 fields together are the primary key, and you have explained that because of that, duplicates will be prevented - no itemsku will have a duplicate date and no date will have a duplicate itemsku. Thnaks to you and all who help. > Patti > [quoted text clipped - 25 lines] > > > > thanks. >In the table design, i saw the litlle key symbol next to itemsku and date >fields, hence my error in referring to primary keys. Hi Patti, The little key symbol does indeed indicate that the field is part of a primary key for the table. So that wasn't an error. I think Jeff was just clarifying terminology. As Jeff indicated, Access will ensure that the group of fields comprising a primary key will be unique. Also, all the fields in a primary key must have a value - Nulls aren't allowed. Armen Stein Microsoft Access MVP www.JStreetTech.com thanks for taking the time to help. it is greatly appreciated. > >In the table design, i saw the litlle key symbol next to itemsku and date > >fields, hence my error in referring to primary keys. [quoted text clipped - 13 lines] > www.JStreetTech.com > |
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