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shapper
Constraint Violating Yak Guru
450 Posts |
 Posted - 2008-03-24 : 13:03:53
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| Hello,I am creating a table where two of the columns are:Social Number ID and Passport ID.Considering both are unique which should I use for Primary Key?Or should I create a ID from both columns? And how?Thanks,Miguel |
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jackv
Master Smack Fu Yak Hacker
2179 Posts |
Posted - 2008-03-24 : 13:14:35
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| If the combination of SocialNumberID and PassportID is unique and enforces the entity integrity of the table , then use the combination , otherwise look for an alternative , such as a single column.Jack Vamvas--------------------Search IT jobs from multiple sources- http://www.ITjobfeed.com |
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visakh16
Very Important crosS Applying yaK Herder
52326 Posts |
Posted - 2008-03-24 : 14:32:39
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| use a table level constraint on combination |
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Michael Valentine Jones
Yak DBA Kernel (pronounced Colonel)
7020 Posts |
Posted - 2008-03-24 : 14:52:16
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| Is this some kind of table for employees?Have you considered that people may not have a Passport ID, or may not have as Social Security Number?You probably would be better with an identity or uniqueidentifier column as the primary key.CODO ERGO SUM |
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jsmith8858
Dr. Cross Join
7423 Posts |
Posted - 2008-03-24 : 15:06:56
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| The one thing you can absolutely rule out is a composite PK of those two columns. How would that make any sense? Why would you want to allow rows with the same SS# but different passport ID's and vice versa?- Jeffhttp://weblogs.sqlteam.com/JeffS |
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shapper
Constraint Violating Yak Guru
450 Posts |
Posted - 2008-03-24 : 15:22:27
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| My idea is to use ID column, INT or UniqueIdentifier, as I always use.I was just wondering of the advantages and disadvantages or using these two fields as Primary Key.Note that in this case all users will have both a Social Number ID and Passport ID. The composite will always be unique.I think that the only advantage will be using less space but ...So I think I will keep using the INT or unique identifier ID column ...Thanks,Miguel |
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Michael Valentine Jones
Yak DBA Kernel (pronounced Colonel)
7020 Posts |
Posted - 2008-03-24 : 15:35:19
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quote:
Originally posted by shapper...Note that in this case all users will have both a Social Number ID and Passport ID. The composite will always be unique...
Famous last words.CODO ERGO SUM |
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jsmith8858
Dr. Cross Join
7423 Posts |
Posted - 2008-03-24 : 16:14:46
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| Again:Why would you want to allow rows with the same SS# but different passport ID's and vice versa?- Jeffhttp://weblogs.sqlteam.com/JeffS |
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Primary Key