Если один DS по постоянной таблице
PHP код:
{
Query query;
Query countQuery;
QueryRun queryRun;
QueryBuildDataSource qbds;
QueryBuildFieldList qbfl;
;
if (fds.queryRun())
query = fds.queryRun().query();
else
query = fds.query();
countQuery = new Query(query);
qbds = countQuery.dataSourceNo(1);
qbfl = qbds.fields();
qbfl.clearFieldList();
qbfl.addField(FieldName2Id(qbds.table(),"MyField"), SelectionField::SUM);
queryRun = new QueryRun(countQuery);
queryRun.next();
return queryRun.getNo(1).(FieldName2Id(qbds.table(),"MyField");
}