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15 Cards in this Set
- Front
- Back
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Field data integrity
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Default value
Range control Null value control Referential integrity (null/range control for foreign/primary keys) |
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Benefit of denormalization
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Improved performance - fewer table lookups
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Cost of denormalization
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Wasted space
Data integrity threats |
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Vertical partitioning and primary keys?
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The primary key column must be repeated
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Advantages of partitioning?
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Efficiency
Local optimization Security, recovery Load balancing Enables parallel processing |
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Disadvantages of partitioning?
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Inconsistent access speed across partitions
Complexity Extra space or update time |
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Factors to consider when choosing file organization
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Data retrieval speed
Space utilization Protection from failure/data loss Security from unauthorized access Need for reorganization Accommodating growth |
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Types of File Organizations
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Indexed - seperate table that contains organization of records for quick retrieval
Hash Sequential |
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Sequential FO
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n/2
If sorted: insert and delete requires resort |
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Hashed FO
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MOD function
Collision - use lists |
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Bitmap index FO
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Rows: Possible values of attributes
Columns: Fields |
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B-tree index
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avg time: depth of tree
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Rules for using indexes (part 1)
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Use on larger tables
Index PK Index WHERE, ORDER BY and GROUP BY Index when >100 values but not when <30 values |
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Rules for using indexes (part 2)
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Don't index fields with long values
Null values will not be referenced Use for non-volatile |
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RAID
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Multiple disks mimic single disk
Can write to disks simultaneously |
