Handle missing records in secondary join files

The system allows you to control whether to allow defaults for missing records in secondary files (similar to the JDFTVAL DDS keyword for a join logical file). You can also specify that only records with defaults be processed. This allows you to select only those records in which there is a missing record in the secondary file.

Example: Handle missing records in secondary join file

This example shows how to read records from the primary file that do not have a record in the secondary file.

In Example 1: Dynamically join database files without DDS, the JDFTVAL parameter is not specified, so the only records read are the result of a successful join from FILEA to FILEB. If you want a list of the records in FILEA that do not have a match in FILEB, you can specify *ONLYDFT on the JDFTVAL parameter as shown in the this example:

OVRDBF     FILE(FILEA) SHARE(*YES)
OPNQRYF    FILE(FILEA FILEB) FORMAT(FILEA) +
              JFLD((CUST FILEB/CUST)) +
              MAPFLD((CUST 'FILEA/CUST')) +
              JDFTVAL(*ONLYDFT)
CALL       PGM(PGME) /* Created using file FILEA as input */
CLOF       OPNID(FILEA)
DLTOVR     FILE(FILEA)

JDFTVAL(*ONLYDFT) causes a record to be returned to the program only when there is no equivalent record in the secondary file (FILEB).

Because any values returned by the join operation for the fields in FILEB are defaults, it is normal to use only the format for FILEA. The records that appear are those that do not have a match in FILEB. The FORMAT parameter is required whenever the FILE parameter describes more than a single file, but the file name specified can be one of the files specified on the FILE parameter. The program is created using FILEA.

Conversely, you can also get a list of all the records where there is a record in FILEB that does not have a match in FILEA. You can do this by making the secondary file the primary file in all the specifications. You can specify:

OVRDBF     FILE(FILEB) SHARE(*YES)
OPNQRYF    FILE(FILEB FILEA) FORMAT(FILEB) JFLD((CUST FILEA/CUST)) +
              MAPFLD((CUST 'FILEB/CUST')) JDFTVAL(*ONLYDFT)
CALL       PGM(PGMF) /* Created using file FILEB as input */
CLOF       OPNID(FILEB)
DLTOVR     FILE(FILEB)

Note: The Override with Database File (OVRDBF) command in this example uses FILE(FILEB) because it must specify the first file on the FILE parameter of the Open Query File (OPNQRYF) command. The Close File (CLOF) command also names FILEB. The JFLD and MAPFLD parameters are also changed. The program is created using FILEB.