Is it possible to have access create primary keys for items by appending a string to the primary key one level above it?
I am trying to create an inventory management database for my company's server ops team, to keep track of things such as switches, servers, UPS's, etc. I have things organized to separate our different locations, the different rooms in said locations, the different racks in said rooms, and finally a 1-1 relationship between an occupied rack U and a device. The primary key for locations would be a simple, 3-letter designation that we use as a site code. The primary key for a room would be that site code plus "-###
" where "###" is the displayed room number. This is to simplify the attributes for the room/lower levels (i originally had an auto-gen number for pKey, with a separate attribute for display number). this would continue down, until the rackU and/or device entities. For them, i'm looking to allow the admins to use a form, select the correct Location, Room, and Rack#, then enter a rackU and serial number/asset tag for the device. Then the rackU primary key would need to generate itself to be the primary key value of its associated rack, plus the U number.
To simplify, I would be manually inputting each entry down to rackU, and primary keys would look like:
[Loc] = ABC
[Room] = [Loc]-###
[Rack] = [Room]-A/1
(some racks are lettered, some are numbered)
Then, when entering a new device, user would select Location, Room, Rack, and input a rackU number. I need some way to auto-generate the rackU primary key to be the linked Rack primary key plus the given U number.
It's one of those things where I'm fairly certain I could make it work if I was writing this database from scratch in python or PHP, or if i was using an actual mySQL database, but I'm completely lost as to how to handle this in Access.
Best Answer
I think the difficultly lies in using the parent table as part of the sub-table's primary key. So long as you have a reference to the parent table, you can always generate a reference that combines Location+Room or Room+Rack. Otherwise the primary key will get too hard to update and you have bad primary key.
I can see two ways to tackle this depending on how many locations, rooms, racks you have. It depends on quantity for your interface.
Firstly, a schema...
...tables for custom devices can extend tblDevice
Foreign keys in square brackets, PK++ means an auto increment primary key.
As you can see, a Location has many Rooms, a Room has many Racks, a Rack has many Devices.
I have made primary keys as auto IDs as I prefer them to be integers and there's less to think about should you change a location/room/rack reference.
Populate this with Locations, Rooms and Racks as appropriate.
Solution 1 :: Not a lot of racks
Solution 2 :: Lots of racks
Have a query similar to:
To generate a list of Location-Room-Rack references.
User selects one, then fills in the information. List will be equal to the number of racks (which could get a bit excessive).
Advantages
Further schema additions
I've used racks in the past, I simplified the schema but these are some additions that spring to mind.
You can then do further validation: if you have a 39U rack and somebody tries to put a 5U device in at location 38, you can throw an error (as U's 40-42 don't exist!). Also if somebody puts a 3U device in at location 10, and something is in location 11, you know it won't fit or they have not updated the details of the device that is no longer there!
You could also make some clever queries that would tell you how much space there is in your racks (and where). But that's beyond the scope of this question!
Hope this helps.