Schema DDL OWNER clause and SEARCH KEY clause
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4.8 Special sets 4.8.1 SYSTEM set
OWNER IS SYSTEM.
A record type which is not related to a higher-ranking record type on the basis of its data
structure can still be declared member of a set.
This applies in the following cases:
– For reasons of sequential processing, the records are to be in a different or der than
ascending order according to database key values (see page 85 and page 94 ff).
– Only a certain collection of records is to be processed (see section “Defining the type
of membership of records in a set” on page 79).
In these cases, the record type is declared member of a set w hich has only a symbolic
owner record type named SYSTEM. Accordingly such set s are called SYSTEM sets.
The symbolic owner record type contains exactly one record whic h is automatically
generated by UDS/SQL. It is called an anchor record. A SYSTEM set thus consists of just
one set occurrence.
In addition to the possibilities of a normal set, SYSTEM sets allow direct access via hash
routines.
Defining secondary keys for conversion by hash routine
SEARCH KEY IS item-name,... USING CALC[ hash-routine]
DUPLICATES ARE[ NOT] ALLOWED
A key declared by SEARCH KEY IS... is a SEARCH key or secondary key. It may be consist
of more than one item.
item-name specifies the item(s) comprising the key. All items must be part of the corre-
sponding member record type.
DUPLICATES ARE[ NOT] ALLOWED specifies whether UDS/SQL is to accept or reject
duplicate key values.