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Studying 70-441 Microsofts Design a database solution
| Question | Answer |
|---|---|
| NORMALIZATION | - the process of eliminating duplicates in a relational database design- converting an entity into tables of progressively smaller degree and cardinality until you reach an optimum level of decomposition |
| What are the Pro's of Normalization? | - the process of eliminating duplicates in a relational database design- You save space by storing data element only once- It's easier to maintain data consistecy because you have only one instance of the data element to maintain |
| What are the Con's of Normalization? | - you need to perform expensive join operations again to retrieve related data- It's possible to over normalize |
| What is the most normal of NF's ("Normal Forms")? | 3rd Normal Form |
| Explain First Normal Form (1NF): | - every column is atomic- it is a valid table, so you separate any repeating groups or multivalued columns- a unique key has been identified for each row- All attributes are functionally dependent on all or part of the key |
| Explain Second Normal Form | - 1NF+ (ALL RULES OF NORMAL FORM, ANDL..) - All non-key attribute are fully functionally dependent on the entire key( you are getting rid of partial entities) |
| What are you looking for when you want to go to 2NF (Second Normal Form)? | 1. Look for composite keys 2. Look for attributes that are dependent on only one of the key columns |
| How to you achieve Third normal form? | 2NF+ (All 2NF rules, and...) Look for transitive dependencies (are there non-key attributes that depend on another nonkey attribute?) |
| De-Normalization | bringing back levels of redundancy to increase database performance |
| Pro's of De-Normalization | - Fewer joins and locks to maintain - Fewer number of calculations for SQL Server to perform |
| Con's of De-Normalization | - Multiple instances of the same data (maintenance and data integrity issues) - Update anomalies will occur |
| Requirements of De-Normalization | 1. data must be up-to-date 1a. Use DML triggers for data that needs to be maintained in real-time. 1b. If 100% accuracy is not important, try running a T-SQL script after hours via SQL Server Agent job 2. data should be non-volatile |
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dianagele
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