Relations of existence of value can be specified for all field types. Simple condition containing these relations does not have operands. In table 26-4 relations of existence admissible for ObjectLand are presented.
Symbol | Name | Requirement for true simple condition |
V | Exists | Not empty field value |
~V | Does not exist | Empty field value |
Table 26-4. Relations of existence
To understand the sence of relations of existence one should recall that the record field can have an empty value. This value is assigned to a field if no value was entered when adding or editing the record.
Using the relation “does not exist” it is possible to find all records for which no field value has been assigned for some reason, that is, one can find records with empty value for this field.
For example, for the operation “find and display records of the table “List of Building Certificates” for which date of repair is not specified” the search condition should be formulated in the following way:
field – “Date of Last Repair”, relation – “does not exist”.
Please pay attention that the simple condition using any other relation except for the relation “does not exist” will be false for records in which the appropriate field has an empty value.
 |  |
