Duration Of Link Established By Link Or Link Optional; Link Statement Considerations - Tandem ENFORM 058057 Reference Manual

Statements
LINK Statement
Duration of Link
Established by LINK or
LINK OPTIONAL Statement
LINK Statement
Considerations
4–26
When you use either the LINK statement or the LINK OPTIONAL statement, you
establish a link that exists for the duration of the ENFORM session. You can clear such
a link by entering one of the following:
a CLOSE statement for one of the record descriptions.
a DELINK statement for the link.
a DICTIONARY statement or a ?DICTIONARY command that clears the entire
internal table. When you clear the internal table, you also clear all links.
ENFORM allows you to specify up to 32 LINK or LINK OPTIONAL statements. If
you include the LINK OPTIONAL statement in your query specifications, be sure to
follow the rules described later in this section under "LINK OPTIONAL Statement
Considerations."
When you use a single LINK statement, ENFORM builds a set of logical records by
searching through the data files associated with the linked record descriptions. A
record from one data file becomes part of the set of logical records only if the content
of its linking field matches the content of the linking field in a record in the other data
file.
When you use a LINK statement, you indicate that the values of the linking fields
must be equal. (If you want to indicate inequality for the values of the linking fields,
you must use a WHERE clause.) A single LINK statement is equivalent to the
following form of the WHERE clause:
WHERE qualified-field-name1 EQ qualified-field-name2,
When you use a LINK statement, the order in which you enter the record description
names is unimportant. For example:
LINK employee.empnum TO branch.manager;
is the same as:
LINK branch.manager TO employee.empnum;
058057 Tandem Computers Incorporated