Relations used in building simple conditions in the structure of filter group condition can be divided into the same four categories like the relations from which search conditions for tables are built, namely: comparison relations, relations of diapasons/intervals, relations of existence and relations of matching the pattern (see chapter 26 “Searching records in a table”, table 26-1).
All relations used when building search condition can be also used for building group condition. Besides, two additional relations of existence can be used, and the meaning and names of relations of existence described above require some modification.
In table 36-1 relations of existence which can be used when building simple conditions as part of filter group condition are enumerated.
Character | Name | Simple condition truth terms |
E | record exists | there is a table record linked with the feature |
~E | record does not exist | there is no table record linked with the feature |
V | value exists | not empty field value of the linked record |
~V | value does not exist | empty field value of the linked record |
Table 36-1. Relations of existence when building filter group condition
All relations of existence do not require operands. It is necessary to specify a name of the linked table and a field name in this table for relations of existence of value, for relations of existence of record only a name of the linked table is enough.
As it was noted above, for all relations, except for relations of existence, absence of the linked record or an empty field value of all linked records included into the simple condition lead to undefined condition value (there is not enough data to check the relation). Relations of existence permit the user to get some definite (true or false) value of simple condition in these cases. See also relation variant COUNT below.
