Answer / aravind9882

index is separate file attached to dataset.
create index on variable that is used in 'by processing'
or 'where processing'.
it will enhance the performance and fast retrieving the
observations when you use indexed variable in where
statement.
you need not to sort the variable if it is indexed when u
use it in "by statement".
create an index on variable when:
-u have to retrieve observations not more than 15% of d
dataset.
-create index on variable where 'by-variable' will have
more than 8 disctint values.

index is of two types:
simple index-created on single variable.
composite index-created on 2 or more variables.
index can b created using proc datasets, proc sql and
datastep.

Answer / abhilash

by using index we search a particular string or sub string
it returns the position where the sub string is located
for ex:
data index;
name="india is greatest country";
idx-index(name,"great");
run;
it returns the great sub string position(10)

Answer / guest

Generally SAS reads The obseravtions in sequentiall manner.
it takes a lot of time .to aviod this we are using index.
ithis index concept usefull when we dealing with large
datsets.

Answer / hari

This is mainly useful for the fast retrival of data (For ex
we have 559 in 1 lac obs then by index we can get the data
with out reading all the observations

Index are 2 type:

1.simple
2.Composite


ex-for simple


proc datasets lib=college;
modify time;
index create class;
run;


ex-for composite:


proc datasets library=college;
modify time;
index create names(=(name school);
run;

Answer / sushil kumar

Index Function is used to search a Character in a String and returns position of the String

Answer / dvsr

Without index if we executed the query it will go to the
full table scan. If any data set or table has the index
first query checks that particular If condition or where
condition in that column then it will go to the remaining
columns.

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0 Answers  

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