December 2014
Intermediate to advanced
858 pages
40h 10m
English
Content preview from SAS Certification Prep Guide, 4th Edition
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Summary
Text Summary
Understanding Indexes
An index is an auxiliary
file that is defined on one or more of a table's columns, which are
called key columns. The index stores the unique column values and
a system of directions that enable access to rows in that table by
index value. When an index is used to process a PROC SQL query, PROC
SQL accesses directly (without having to read all the prior rows)
instead of sequentially.
You can create two types
of indexes:
-
simple index (an index on one column)
-
composite index (an index on two or more columns).
You can define either
type of index as a unique index, which requires that values for the
key column(s) be unique for each row.
Deciding Whether to Create an Index
When deciding whether ...
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