Sounds like you need a 1:N relationship table to hold userInfo separate from either the user or group table. Adding a infoIdentifier would allow the number of rows added for a specific user to be sized based on the specific user needs. This is effect would be the "key" part of a key-value pair, normally associated with associative arrays. The userSpecificInformation would hold the value portion of the information.
UserInfo table: id (pk) user_id (fk) infoIdentifier userSpecificInformation > user table: > id (pk) > name > any other user info only dependant on the user > > group table: > id (pk) > name > > usergroup table: > user_id (pk) > group_id (pk) > any info specific to individual user/group combo UserInfo table: id (pk) user_id (fk) infoIdentifier userSpecificInformation -----Original Message----- From: Eric Gorr [mailto:[EMAIL PROTECTED] Sent: Saturday, April 02, 2005 2:59 PM To: Tom Crimmins Cc: mysql@lists.mysql.com Subject: Re: [Q] Database design Tom Crimmins wrote: > user table: > id (pk) > name > any other user info only dependant on the user > > group table: > id (pk) > name > any other group info only dependant on the group > > usergroup table: > user_id (pk) > group_id (pk) > any info specific to individual user/group combo Yes, if I understand what you are saying here correctly, I considered this. However, the problem is that the columns corresponding to "any info specific to individual user/group combo" is not guaranteed to be consistent across groups. Well, to be more precise, the type for each column will be the same, but the number of required columns (call this number N) will be different. It is for this reason that it seemed necessary to have a separate table per group. Now, if I could decide what the maximum number of required columns would be, then I could see using this design, but this is simply not possible. I am, of course, limited by the maximum number of columns (call this number X) allowed within a mySQL database. The required number of columns for a particular group could be anywhere between 1 and X. However, it just seemed like a bad idea to use that large of a table when the vast majority of it would go unused and much of it would likely never be used at all. But, perhaps I am wrong and it would simply not be an issue. I suppose it would be possible to dynamically size 'usergroup table' based on the current max N across all groups. Basically, if N changes for a particular group, look at the value of N for all groups, take the max and size 'usergroup table' accordingly. Is this what you would do? -- MySQL General Mailing List For list archives: http://lists.mysql.com/mysql To unsubscribe: http://lists.mysql.com/[EMAIL PROTECTED] -- MySQL General Mailing List For list archives: http://lists.mysql.com/mysql To unsubscribe: http://lists.mysql.com/[EMAIL PROTECTED]
