About relationships using comparative operators
In a comparative relationship, you use one or more of the following operators to compare match field values in the two related tables. The relationship returns related records when the comparison evaluates successfully, according to the criteria you establish.
For example:
Two tables with lines between two fields showing a relationship based on the greater-than comparative operator
In this relationship, DateFieldC and DateFieldD are match fields. Records in TableD are related to records in TableC that have a later DateFieldC value. Records in TableC are related to records in TableD that have an earlier DateFieldD value. For example, if a record in TableC has a DateFieldC value of 12/11/2014, all the records in TableD with a DateFieldD value of 12/10/2014 or earlier are related to it. In TableD, if a record has a DateFieldD value of 12/11/2014, all records in TableC with DateFieldC values of 12/12/2014 or later are related to it.
Related topics 
About single-criteria relationships
About multi-criteria relationships
About relationships that return a range of records
About self-joining relationships