Comparison Of The Link Statement, The Link Optional Statement, And The Where Clause; Table C-1. Truth Table - Tandem ENFORM 058057 Reference Manual

LINKS and the LINK OPTIONAL Statement Rules

Comparison of the LINK Statement, the LINK OPTIONAL Statement, and the WHERE Clause

Comparison of the LINK Statement, the LINK OPTIONAL Statement, and the WHERE Clause
C–12
Table C-1 contains a truth table that compares the LINK statement, the LINK
OPTIONAL statement, and the WHERE clause.

Table C-1. Truth Table

Establishes a session-wide link.
Establishes a two-directional link.
Can link more than two record
descriptions.
The order in which you specify record
description names is unimportant.
Builds logical records from matching
records in the data files associated with
all linked record descriptions
Builds logical records by preserving the
data from the data file associated with
the record description name on the left
side.
058057 Tandem Computers Incorporated
LINK LINK OPTIONAL
Statement Statement
True True
True False
False False
False True
True False
False True
WHERE
Clause
False
True
True
True sometimes
(The order is
unimportant if you
link record
descriptions by
specifying that their
linking field values
must be equal.)
True
False