SAS study notes: index in sas: when to use index, how to create index, how to modify index / datasets / variables without losing index

Index

When to use index:

1: yield faster access to small subsets of obs for WHERE processing

2: return obs in sorted order for BY processing

3: perform table lookup operations

4: join obs

5: modify obs

Simple index: (index=(myindex)) or (index=(lastname firstname))

Composite index: (index=(comp_index=(lastname firstname)))

Pcoc datasets library=libref;

Modify sas_data_set;

Index delete index_name;

Index create index_specification;

Quit;

Proc sql;

Create index index_name on table_name;

Drop index index_name from table_name;

Quit;

Task	Effect
Add observation(s) to data set	Value/identifier pairs are added to index(es).
Delete observation(s) from data set	Value/identifier pairs are deleted from index(es).
Update observation(s) in data set	Value/identifier pairs are updated in index(es).
Delete data set	The index file is deleted.
Rebuild data set with DATA step	The index file is deleted.
Sort the data in place with the FORCE option in PROC SORT	The index file is deleted.

Use PROC DATASETS to copy, rename(change) datasets, rename variables

DATA SAS-data-file-name (INDEX=

(index-specification-1</UNIQUE><...index-specification-n</UNIQUE>>));

SET SAS-data-set-name ;

RUN;

PROC DATASETS LIBRARY=libref ;

MODIFY SAS-data-set-name;

INDEX DELETE index-name ;

INDEX CREATE index-specification;

QUIT;

PROC SQL;

CREATE INDEX index-name

ON table-name(column-name-1<...,column-name-n>);

DROP INDEX index-name FROM table-name ;

QUIT;

PROC CONTENTS DATA=SAS-data-set-name;

RUN;

PROC DATASETS <LIBRARY=libref> ;

CONTENTS DATA=SAS-data-set-name;

QUIT;

PROC DATASETS LIBRARY=old-libref ;

COPY OUT=new-libref;

SELECT SAS-data-set-name;

QUIT;

PROC COPY OUT=new-libref IN=old-libref ;

SELECT SAS-data-set-name(s);

RUN;

QUIT;

PROC DATASETS LIBRARY=libref ;

CHANGE old-data-set-name = new-data-set-name;

QUIT;

PROC DATASETS LIBRARY=libref ;

MODIFY SAS-data-set-name;

RENAME old-var-name-1 = new-var-name-1 ;

<...old-var-name-n = new-var-name-n> ;

QUIT;