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What is a Predetermined join field?

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What is a Predetermined join field?

Post  maran on Sun Oct 14, 2012 11:25 pm

A Predetermined Join Field is used to hold the result of various operations performed on information retrieved from the file nominated by the access route. It must be defined in the Data Dictionary.
The type of operations available to be performed depend on the relationship between the files as indicated by the number of records expected on the access route definition.
The operations are TOTAL, MAXIMUM, MINIMUM, AVERAGE, COUNT, and LOOKUP.
When the relationship is 1 to 1, (number of records 1) using the key defined on the access route a single value will be retrieved into the Predetermined Join Field. For example a product description can be retrieved using the product code if an access route has been defined between an order line file and a product file. A "keep last" value can be nominated to reduce I/Os.
When the relationship is 1 to many (number of records greater than 1) the Predetermined Join Field will hold the result of the selected operation on the selected field in the file nominated by the access route, retrieved using the key in the access route definition. For example the total of the line values from an order line file could be retrieved for display with the order header file
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