IDXNAME= Table Option

Directs SAS to use a specific index to match the conditions of a WHERE clause.

Category:	User Control of SAS Index Usage
Restrictions:	Use with input data sets only
Restrictions:	Cannot be used with the IDXWHERE= table option
Data source:	SAS data set

Syntax

Syntax

IDXNAME= index-name

Arguments

index-name

specifies the name (up to 32 characters) of a simple or composite index for the SAS data set. SAS does not attempt to determine whether the specified index is the best one or whether a sequential search might be more resource efficient.

Interaction

The specification is not a permanent attribute of the data set and is valid only for the current use of the data set.

Details

By default, to satisfy the conditions of a WHERE clause for an indexed SAS data set, SAS identifies zero or more candidate indexes that could be used to optimize the WHERE clause. From the list of candidate indexes, SAS selects the one that it determines will provide the best performance, or rejects all of the indexes if a sequential pass of the data is expected to be more efficient.

Because the index that SAS selects might not always provide the best optimization, you can direct SAS to use one of the candidate indexes by specifying the IDXNAME= table option. If you specify an index that SAS does not identify as a candidate index, then IDXNAME= table option does not process the request. That is, IDXNAME= does not allow you to specify an index that would produce incorrect results.

Comparisons

The IDXWHERE= table option enables you to override the SAS decision about whether to use an index.

Example

This example uses the IDXNAME= table option to direct SAS to use a specific index to optimize the WHERE clause. SAS then disregards the possibility that a sequential search of the data set might be more resource efficient and does not attempt to determine whether the specified index is the best one. (Note that the EMPNUM index was not created with the NOMISS option.)

create table mydata.empnew
   as select * from mydata.employee {option idxname=empnum}
   where empnum < 2000;

IDXNAME= Table Option

Syntax

Arguments

index-name

Details

Comparisons

Example

See Also