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KazaX
Starting Member
28 Posts |
 Posted - 2008-11-24 : 12:58:44
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| helloif I have a table R(A,B,C) and AB is key for that relation. if I create a table S by selecting just A and B from R. what will be the key for table S ??? AB itself or there is no key for relation S???And does it satisfy 3NF?Thanks. |
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pbguy
Constraint Violating Yak Guru
319 Posts |
Posted - 2008-11-24 : 22:50:34
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| Any reason for another table? because the R table itself uniquely identify the rows since it is having keys A,B. If u create another table S by extracting columns A,B from R will give the same no. of rows from R.--------------------------------------------------S.Ahamed |
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KazaX
Starting Member
28 Posts |
Posted - 2008-11-25 : 06:40:58
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quote:
Originally posted by pbguy
Any reason for another table? because the R table itself uniquely identify the rows since it is having keys A,B. If u create another table S by extracting columns A,B from R will give the same no. of rows from R.--------------------------------------------------S.Ahamed
Yes, I just want to know, would AB still be a key in new table ? |
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byrmol
Shed Building SQL Farmer
1591 Posts |
Posted - 2008-11-25 : 15:30:11
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| Yes. Every relation must have a key.DavidM |
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FD