Studying 70-441 Microsofts Design a database solution
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| 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
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| 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
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| 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
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| What is the most normal of NF's ("Normal Forms")? | 3rd Normal Form
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| 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
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| 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)
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| 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
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| 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?)
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| De-Normalization |
bringing back levels of redundancy to increase database performance
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| Pro's of De-Normalization | - Fewer joins and locks to maintain
- Fewer number of calculations for SQL Server to perform
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| Con's of De-Normalization | - Multiple instances of the same data (maintenance and data integrity issues)
- Update anomalies will occur
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| 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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To hide a column, click on the column name.
To hide the entire table, click on the "Hide All" button.
You may also shuffle the rows of the table by clicking on the "Shuffle" button.
Or sort by any of the columns using the down arrow next to any column heading.
If you know all the data on any row, you can temporarily remove it by tapping the trash can to the right of the row.
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