This Slideshare presentation is a partial preview of the full business document. To view and download the full document, please go here: http://flevy.com/browse/business-document/the-complete-guide-to-dba-practices-and-procedures-database-design-part-4-575 Part 4 of a multi-part series of presentations on the management discipline of database administration. This part focuses on designing effective and efficient databases. The entire series can be used to implement an efficient and effective database administration function at your organization. This first part covers the following areas: - From Logical Model to Physical Database - Database Performance Design - Denormalization - Views - Data Definition Language - Temporal Data Support

1. Database Administration:
The Complete Guide to Practices and Procedures
Chapter 4
Database Design

2. Physical Database Design
Requirements
• In-depth knowledge of the database objects supported by
the DBMS and the physical structures and files required to
support those objects
• Details regarding the manner in which the DBMS supports
indexing, referential integrity, constraints, data types, and
other features that augment the functionality of database
objects
• Detailed knowledge of new and obsolete features for
particular versions or releases of the DBMS
• Knowledge of the DBMS configuration parameters that are
in place
• Data definition language (DDL) skills to translate the
physical design into actual database objects
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3. Transform Entities to Tables
• First general step:
– Map each entity in the logical data model to a
table in the database
• Things may, or may not, be that easy
– Denormalization?
PAYMENT
Payment Transaction Num
Type
Amount
PaymentDate
Status
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4. Nulls
http://craigsmullins.com/dbta_043.htm
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5. Determine Row Size
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6. Storage Planning
• Start by determining how many rows are
required
• Calculate the row size (discussed earlier)
• Figure out the number of rows per block/page
• Multiple #rows/page by the page size
• This gives you the size of the object
• Except for free space…
http://craigsmullins.com/dbta_110.htm
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7. Database Performance Design
• Designing Indexes
– Partitioning
– Clustering
• Hashing
• Interleaving Data
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8. Bitmap Index
Identifier Gender Bitmap
1 Female 0110000010
2 Male 1000011101
3 Unknown 0001100000
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9. Clustering
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10. Denormalization
• Prejoined Tables - when the cost of joining is prohibitive
• Report Tables - for specialized critical reports (e.g. CEO)
• Mirror Tables - when two types of environments require concurrent access to
the same data (OLTP vs DSS)
• Split Tables - when distinct groups/apps use different parts of the same table
– Splitting columns across two tables for long variable character columns.
• Combined Tables - to eliminate one-to-one relationships
• Redundant Data - to reduce the number of joins for a single column (e.g.
definitional, CA to California)
• Repeating Groups - to reduce overall I/O (& possibly DASD)
• Derivable Data - to eliminate calculations & aggregations
• Speed Tables - to support hierarchies
• Physical Implementation Needs – e.g.) to reduce page size
http://www.tdan.com/view-articles/4142
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11. The Goal!
Normalized vs. Denormalized
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12. View Usage Rules
• Security - row and column level
• Access - efficient access paths
• Data Derivation - put the calculations in the view
• Mask Complexity - hide complex SQL from users
• Rename a Table
• Column Renaming - table with better column
names (easier to use than AS)
• Synchronize all views with base tables...
DO NOT USE ONE VIEW PER BASE TABLE!
http://craigsmullins.com/dbta_115.htm
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13. • Business Time (aka application time or valid time)
– Specifies when the facts stored in the database
are true with respect to the real world.
– These are the dates of interest to the business
user interacting with the data.
– Business time is useful for only certain types of data
that change over time and the validity of the data is
relevant to the application and users.
• System Time (aka transaction time)
– Denotes the time when the fact became current in the database.
– System time can be used to track the insertion and modification history of
the data.
– Unlike business time, transaction time may be associated with any
database entity.
Temporal Data:
Business Time vs. System Time
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14. Questions
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15. 1
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