July 2010
Intermediate to advanced
448 pages
12h 22m
English
Content preview from Physical Database Design
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194 CHAPTER 10 Counting and Data Sampling in Physical Design Exploration
10.4 Summary
Counting is a key aspect of physical database design in terms of understanding
• The number of distinct values of a column or a set of columns to be used as a
design attribute, such as index keys, partitioning columns, MDC columns, etc.
• The absolute number of rows in a table or materialized view.
• The ratio of unique values to total rows.
The SQL language supports counting naturally through the COUNT and DIS-
TINCT keywords, making it possible to exploit the power of SQL to help design the
database. Exploration can be dramatically sped up by the use of sampling. ...
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