Here is a simple example of a SQL SELECT from the table se_lt_x
test(A) :-
format('About to call CQL with A=~w', [A]),
{[],
se_lt_x :: [a-A,
b-B,
c-C]},
format('B=~w, C=~w', [B, C]).
- The CQL is distinguished from the ordinary Prolog by appearing in
curly brackets
- Prolog variables which are ground when the CQL is executed will
appear in the resulting SQL as part of the WHERE clause
Comparisons can be done in-line e.g.
[a-'ELSTON_M']
or with the == operator e.g.
[a-A], A == 'ELSTON_M'.
The single = operator means unify, not compare. Use = for
unification, not comparison
FIXME: Unification is deprecated.
The operators =:= and \== are also
available for numerical value comparisons (they just translate to SQL =
and <>, so in fact you could use them for string
comparisons)
