What Are The Candidate Keys? - Programming - Nairaland
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| What Are The Candidate Keys? by eazyd(m): 9:52pm On Feb 18, 2012 |
Please open the attachment to view the table. Is this correct? Answers to questions like these are based on different views and opinions, so i'm putting this out to see if my views tally with yours. 1a- Studentid--->StudentName CourseNumber --->CourseName 1b- Studentid --->StudentName Very unlikely because a student can have different studentid. CourseNumber --->CourseName Very likely because no two same course can have same course number. 1c- None 1d- The table is not well formed because the determinants (Studentid,CourseNumber) are not candidate keys. Also the table can be broken into 2 tables to be well-formed.
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| Re: What Are The Candidate Keys? by okeyxyz(m): 5:25am On Feb 19, 2012 |
1a) is correct. 1b) is wrong. a student cannot have two ids, what u see are two students who happen to have the same names but each can be uniquely identified by her student_id |
| Re: What Are The Candidate Keys? by eazyd(m): 9:45pm On Feb 19, 2012 |
@okey Thanks for your advise but what bout the candidate keys and if the table is well formed or not. Based on functional dependencies i think the table is well formed but in Normalization, the table isn't well formed. What do you think? |
| Re: What Are The Candidate Keys? by okeyxyz(m): 12:03am On Feb 20, 2012 |
candidate keys are keys that uniquely identify records, in this case: studentID for a student table & CourseNumber for a course table. doing a quick google search suggests that a well-formed table is one that meets the first-normal-form(no repeating columns), so based on that, i'd say it's well-formed. |
| Re: What Are The Candidate Keys? by eazyd(m): 1:23am On Feb 20, 2012 |
what about recordid? |
| Re: What Are The Candidate Keys? by okeyxyz(m): 1:28am On Feb 20, 2012 |
eazyd: it depends on wether it's useful to you or u want to discard it. if it's useful, then it's a candidate key. |
| Re: What Are The Candidate Keys? by eazyd(m): 2:07am On Feb 20, 2012 |
im askin for your opinion, do you think its useful? |
| Re: What Are The Candidate Keys? by okeyxyz(m): 10:24am On Feb 20, 2012 |
i would't use it for anything. therefore discard! |
| Re: What Are The Candidate Keys? by niharikaclark: 7:45am On Feb 21, 2012 |
Candidate key is the set of attribute that is use for make a primary key.a candidate key of a relation is a minimal superkey for that relation |
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