The signs 
and 
before table names on page “Joins” of the property sheet indicate the character of the correspondence between records of two base tables.
The sign denotes that there is “one-to-one” correspondence between joined table records, that is, only one record of one table corresponds to every record of the other table.
It is possible to guarantee such a correspondence by specifying the attribute of uniqueness for the fields by which join is performed. In other words, the presence of the sign denotes that both fields by which join is performed have the attribute of uniqueness.
The join of the type “one-to-many” is obtained if the join field has the attribute “Unique” in the root table (to which tables are joined), and the join field in the joined table does not have this attribute. The join of the type “many-to-many” can be obtained when join fields not having the attribute of uniqueness are used.
In case of join of the type “one-to-many” or “many-to-many” the sign will be present before the name of the joined table.
It is possible to perform adding, editing and removing records in the table browser window only in the case if the join has the character “one-to-one”.
It should be noted that when join records are edited changes are entered in the corresponding records of base tables.
If the join does not belong to the type “one-to-one”, then modification of records is impossible. It is explained by the fact that in this case one and the same record of the base table may appear in more than one join record and changing such a record may cause changing of other join records.
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