SAS 9.4 Language Reference, 6th Edition

Listing Integrity Constraints . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 642

Rejected Observations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 642

Integrity Constraints and CEDA Processing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 643

Examples . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 643

Understanding SAS Indexes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 649

Definition of SAS Indexes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 649

Benefits of an Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 650

The Index File . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 650

Types of Indexes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 651

Deciding Whether to Create an Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 653

Guidelines for Creating Indexes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 655

Creating an Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 657

Using an Index for WHERE Processing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 659

Using an Index for BY Processing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 665

Using an Index for Both WHERE and BY Processing . . . . . . . . . . . . . . . . . . . . . . 666

Specifying an Index with the KEY= Option for SET and MODIFY Statements . . 667

Taking Advantage of an Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 667

Procedures and SAS Operations That Maintain Indexes . . . . . . . . . . . . . . . . . . . . 667

Extended Attributes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 671

Definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 671

Enabling and Manipulating Extended Attributes . . . . . . . . . . . . . . . . . . . . . . . . . . 671

Compressing Data Files . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 672

Definition of Compression . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 672

Requesting Compression . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 673

Disabling a Compression Request . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 673

Definition of a SAS Data File

A SAS data file is a type of SAS data set that contains both the data values and the

descriptor information. SAS data files have the member type of DATA. There are two

general types of SAS data files:

native SAS data file

stores the data values and descriptor information in a file that is formatted by SAS.

interface SAS data file

stores the data in a file that was formatted by software other than SAS. SAS provides

engines for reading and writing data from files that were formatted by software such

as ORACLE, DB2, Sybase, ODBC, BMDP, SPSS, and OSIRIS. These files are

interface SAS data files, and when their data values are accessed through an engine,

SAS recognizes them as SAS data sets.

Note: The availability of engines that can access different types of interface data

files is determined by your site licensing agreement. See your system

administrator to determine which engines are available. For more information

about SAS Multi Engine Architecture, see Chapter 37, “SAS Engines,” on page

745.

616 Chapter 28 • SAS Data Files