Thread: some Database Questions
08-17-13, 15:56 #1Registered User
- Join Date
- Aug 2013
Unanswered: some Database Questions
Need help answering the following questions. Have a presentation to do and any info will help. I appreciate any help.
1.What key mathematical property of a field is used in deciding if it should belong to an index?
2. What is the general class of dependencies which uniquely identify every record in a table?
3.You are given a table (A, B, C) where A is a low-cardinality attribute, B is a high-cardinality attribute, C is a numerical variable. You're asked to produce cross-tabulation of sum of C by both A and B and show resultant table in Excel spreadsheet. Would you choose to show A as columnar dimension? Why?
08-17-13, 20:18 #2Resident Curmudgeon
Provided Answers: 54
- Join Date
- Feb 2004
- In front of the computer
In theory, theory and practice are identical. In practice, theory and practice are unrelated.
- Divisibility by at least one prime number. If a number is not evenly divisible by at least one prime, it will be very difficult to index.
- Database 101 is the class that covers the dependancies for uniquely identifying every tuple, and by extension every record in a file.
- Yes, because it will minimize the number of rows in the result set which makes the Excel spreadsheet easier to use.