The index that is specified is based on one column, so it is a simple index. In the CREATE INDEX statement, you specify the index name after the keywords CREATE INDEX. You do not include a keyword to specify that this is a simple index. The name of the key column is specified in parentheses after the table name. The name of a simple index must be the same as the name of the key column.

To create a unique index, the UNIQUE keyword is added to the CREATE INDEX statement, between the keywords CREATE and INDEX.

A composite index is based on two or more columns. In the CREATE INDEX statement, you specify the index name after the keywords CREATE INDEX. You do not include a keyword to specify that this is a composite index. The names of the key columns are specified in parentheses after the table name. The name of a composite index cannot be the same as the name of any columns in the table.

Specifying the option MSGLEVEL=I causes informational messages about index usage to be written to the SAS log.

The DROP INDEX statement drops one or more specified indexes from a table. You specify the name of each index to be dropped after the keywords DROP INDEX. The table name is specified after the keyword FROM. The type of index and the names of the indexed columns are not specified in the statement.

The DESCRIBE TABLE statement lists all indexes for one or more tables that you specify, along with other information about the table(s).

The IDXWHERE=YES data set option tells SAS to use the best available index, even if the index does not optimize performance.

Indexes can be created on either character or numeric columns.

Using an index will optimize specific classes of PROC SQL queries. A query in which the key column is specified only in a SELECT clause is not one of these queries.

The IDXNAME= data set option directs PROC SQL to use an index that you specify. The specified index must exist and must be suitable by having at least its first or only column match the condition in the WHERE expression.