All queries examined in the previous chapters were built by selecting separate fields or records of the base tables using the operations of hiding fields and search. The values of record fields of base tables fully correspond to the values of record fields browsed in the window.
However, very often there are requests connected with calculation of some totals based on values of record fields. For example, the following requests can be formulated for the table “List of Building Certificates” (table 22-1 and figure 23-2):
“how many inhabitants are there in Sea Lane?”;
“how many inhabitants are there in every street?”;
“how many buildings are there in every street?”;
“how many inhabitants are there in buildings of municipal and non-municipal housing in every street of the city?”.
ObjectLand provides the possibility to get answers to such requests.
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