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FAQ: What are the methods for record searches during a RELATE or JOINITEM?

Question

What are the methods for record searches during a RELATE or JOINITEM?

Answer

The method used to find matching records in two files during a RELATE or JOINITEM is dependent on the order and structure of the records in the files. The method choice can become important when you have very large files.

The four methods are as follows:

Linear This is the slowest yet simplest method available. For each record, the relational records are scanned until a match is found. The records do not have to be sorted into any particular order. The common item must be in both themes and have the same item definition.

Ordered This method takes advantage of the related tables being sorted on the common item that exists on both tables. It is faster because it is a binary search. The binary search will split the number of records in half after each search.

Link This is the fastest search method available. First, the table must contain an item whose value will directly access the record number in the related table.

Table This is used when the related table is being used to categorize the data in the first table. Instead of looking for an exact match, it will match selected records with the related record, indicating the upper value of the range in which the value will fall.