SPSS® 12.0 Command Syntax Reference

Example
* Reading a keyed file: reading selected records.
KEYED DATA LIST 785
GET FILE=STUDENTS/KEEP=AGE,SEX,COURSE.
FILE HANDLE COURSES/ file specifications.
STRING #KEY(A4).
COMPUTE #KEY = STRING(COURSE,N4). /* Create a string key
KEYED DATA LIST FILE=COURSES KEY=#KEY IN=#FOUND NOTABLE
/PERIOD 13 CREDITS 16.
SELECT IF #FOUND.
LIST.
• GET reads the STUDENTS file, which contains information on students, including a course
identification for each student. The course identification will be used as the key for
selecting one record from a file of courses.
• The FILE HANDLE command defines a file handle for the file of courses.
• The STRING and COMPUTE commands transform the course identification from numeric
to string for use as a key. For keyed files, the key variable must be a string.
• KEYED DATA LIST uses the value of the newly created string variable #KEY as the key to
search the course file. If a record that matches the value of #KEY is found, #FOUND is set
to 1; otherwise, it is set to 0. Note that KEYED DATA LIST appears outside an input program
in this example.
• If the course file contains the requested record, #FOUND equals 1. The variables PERIOD
and CREDITS are added to the case and the case is selected via the SELECT IF command;
otherwise, the case is dropped.
• LIST lists the values of the selected cases.
• This example shows how existing cases can be updated on the basis of information read
from a keyed file.
• This task could also be accomplished by reading the entire course file with DATA LIST
and combining it with the student file via the MATCH FILES command. The technique
you should use depends on the percentage of the records in the course file that need to
be accessed. If fewer than 10% of the course file records are read, KEYED DATA LIST is
probably more efficient. As the percentage of the records that are read increases,
reading the entire course file and using MATCH makes more sense.
FILE Subcommand
FILE specifies the handle for the direct-access or keyed data file. The file handle must have
been defined on a previous FILE HANDLE command (or, in the case of the IBM OS environment,
on a DD statement in the JCL).
KEY Subcommand
KEY specifies the variable whose value will be used as the key. This variable must already
exist as the result of a prior DATA LIST, KEYED DATA LIST, GET, or transformation command.