In the table “List of Building Certificates” described above the field “Street” was made a string one, which is quite logical. However, such a decision causes several inconveniences:
when adding and editing records, errors of entering street names may arise;
it is necessary to enter long names as many times as the number of buildings in the street;
if the street is renamed, the change should be made in all records;
memory usage is unpractical – the street name is stored as many times as the number of records which contain this name.
It is possible and even highly recommended to act in a different way – store only the numeric code of the street from the reference table of streets in the table “List of Building Certificates” (the field “Street”), not the full street name. A table with two columns: numeric street code and street name will be a reference of streets.
However, having performed the actions described above, we will create new difficulties. Now when adding records into the table “List of Building Certificates” and browsing it, it is required to have a reference table of streets before your eyes to associate the code with the street name.
It is possible to overcome these difficulties though. ObjectLand can perform the required association automatically.
The table should have a certain structure so that is could be used as a reference. The reference table should have two fields at least. One of these fields – reference key should have the attribute “Unique” and should be of the same type as the table field to which the reference is set. Values of the key field should correspond to the values in the table field to which the reference is set. The second field – reference value should contain the value substituting the key field in display. There are no limitations on field types in the reference table.
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