Schema DDL Types of access
U929-J-Z125-9-76 93
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Defining a secondary key for direct access via table
SEARCH KEY IS item-name,... USING INDEX [NAME IS name]
DUPLICATES ARE[ NOT] ALLOWED
A key declared by SEARCH KEY IS... is a SEARCH key or secondary key. It may be made
up of more than one item.
item-name specifies the item(s) comprising the key. All items must be part of the corre-
sponding record type.
name specifies the name of the table. This name is referred to in the SSL s tatements
concerning the table.
DUPLICATES ARE [NOT] ALLOWED specifies whether UDS/SQL is to accept or reject
duplicate key values.
Based on this definition, UDS/SQL sets up a record SEARCH key table. This table contains
the values of the secondary keys of all records of a record type, representing a unique
reference between key value, database key value and physical address of the record. The
physical address is not automatically updated, however, when the position of the record is
changed.
A SEARCH key table is used only for direct access to the records of a record type. It always
involves several levels in order to speed up access.
Several independent secondary keys can be defined for one record type.