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Vishian
Starting Member
3 Posts |
 Posted - 2007-02-01 : 19:42:36
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| Hello, I am taking a Database course this semester and I am totally clueless on the general concepts of managing a database. I have a few questions about these two tables. If someone could please answer them and maybe explain it to me I would greatly appreciate it!...and yes it is homework but I really want to understand it!1.Which column or columns contain redundant data?2.Why would you want this duplication, give an example of a use of this database that would benefit from redundancy. 3.Give an example of a specific constraints you would place on programs that accessed this database to control the redundancy?PERSONID NAME DEPT GENDERSC937 Kirk CMD MSM105 McCoy MED MSE602 Rand CMD FSE197 Scott ENG MS179 Spock SCI MSC835 Sulu CMD MSE213 Spock ENG FHello, I am taking a Database course this semester and I am totally clueless on the general concepts of managing a database. GRADEBOOKPERS NAME DEPT DATE COURSE GRADES179 Spock SCI 12/1/2252 CSCI1100 ASC835 Sulu CMD 1/30/2266 CSCI1100 A-SC937 Kirk CMD 1/11/2266 CSCI1100 D S179 Spock SCI 12/1/2286 CSCI4127 ASC835 Sulu CMD 12/1/2286 CSCI1701 B+SC937 Kirk CMD 12/1/2286 CSCI1100 C+SE197 Scott ENG 12/1/2286 CSCI1100 ASE213 Spock ENG 12/1/2286 CSCI1100 ASM105 McCoy MED 12/1/2286 CSCI1100 C |
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nr
SQLTeam MVY
12543 Posts |
Posted - 2007-02-02 : 09:21:33
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| 1. Redundant data in this case is data that appears in both tables. There is a key value which enables you to link the tables but also other data has a copy in multiple rows in one of the tables which isn't necessary. You should be able to spot what it is.2. It is usually done for performance - I would be surprised if it would help in this case though. I'm guessing they are talking about a search for the redundant data but that would probably be slower than using the relationship. Maybe if one of the tables was locked by another process.3. Have a look at foreign keys.==========================================Cursors are useful if you don't know sql.DTS can be used in a similar way.Beer is not cold and it isn't fizzy. |
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Michael Valentine Jones
Yak DBA Kernel (pronounced Colonel)
7020 Posts |
Posted - 2007-02-02 : 11:05:36
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| "2.Why would you want this duplication..."It will keep future generations of DBAs busy fixing the mess it creates.CODO ERGO SUM |
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X002548
Not Just a Number
15586 Posts |
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newbie needs 3 simple answers!