Select records without using DDS

Dynamic record selection allows you to request a subset of the records in a file without using data description specifications (DDS).

For example, you can select records that have a specific value or range of values (for example, all customer numbers between 1000 and 1050). The Open Query File (OPNQRYF) command allows you to combine these and other selection functions to produce powerful record selection capabilities.

• Select records using the Open Query File (OPNQRYF) command
  These topics provide examples of selecting records using the Open Query File (OPNQRYF) command.
• Specify a keyed sequence access path without using DDS
  The dynamic access path function allows you to specify a keyed access path for the data to be processed. If an access path that can be shared already exists, the system can share it. If a new access path is required, it is built before any records are passed to the program.
• Specify key fields from different files
  A dynamic keyed sequence access path over a join logical file allows you to specify a processing sequence in which the keys can be in different physical files (DDS restricts the keys to the primary file).
• Dynamically join database files without DDS
  The dynamic join function allows you to join files without having to first specify data description specifications (DDS) and create a join logical file.
• 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.
• Unique-key processing
  Unique-key processing allows you to process only the first record of a group. The group is defined by one or more records with the same set of key values. Processing the first record implies that the records you receive will have unique keys.
• Define fields derived from existing field definitions
  Listed here are the operations allowed by defining fields derived from existing field definitions.
• Handle the divide-by-zero errors
  Dividing by zero is considered an error by the Open Query File (OPNQRYF) command. This topic discusses how to handle the divide-by-zero error in case that you want a zero answer.
• Summarize data from database file records (grouping)
  The group processing function allows you to summarize data from existing database records.
• Final total-only processing
  Final-total-only processing is a special form of grouping in which you do not specify grouping fields. The output is only one record. All of the special built-in functions for grouping can be specified. You can also specify the selection of records that make up the final total.
• Control how the system runs the Open Query File (OPNQRYF) command
  The optimization function allows you to specify how you are going to use the results of the query.