Use CREATE INDEX

Use the CREATE INDEX statement to create an index on one or more columns in a table and, optionally, to cluster the physical table in the order of the index. This section describes some of the options available when you create indexes. For more information about the CREATE INDEX statement, see the Informix® Guide to SQL: Syntax.

CREATE TABLE customer
(
   cust_num   SERIAL(101) UNIQUE
   fname      CHAR(15),
   lname      CHAR(15),
   company    CHAR(20),
   address1   CHAR(20),
   address2   CHAR(20),
   city       CHAR(15),
   state      CHAR(2),
   zipcode    CHAR(5),
   phone      CHAR(18) 
);

CREATE INDEX lname_index ON customer (lname);