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| SYSTEM 2000 Software |
SYSTEM 2000 Indexing
One of the specifications when defining a schema item is whether SYSTEM 2000 is to create an index of its values. SYSTEM 2000 uses the indexes to access the appropriate data records quickly and efficiently.
A schema item for which an index is created is a key item, implying that it provides easy access to data records that contain its values. Therefore, a key item has an associated index of every distinct value that occurs for the schema item. However, key values do not have to be unique, and there can be many key items in a database definition, or none.
If a schema item is defined as non-key, its values are not indexed, but the values can be searched sequentially.
In addition, you can create or delete an index of values by using the CREATE INDEX and REMOVE INDEX statements in SYSTEM 2000. Using these statements, SYSTEM 2000 automatically changes the specified item to key or non-key. (For information about these statements, see the SYSTEM 2000 CONTROL Language manual.)
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