Помогите с запросом

[Cardagant]

Попробуйте так:

qbdsA = query.addDataSource(tablenum(A));
qbdsA.addRange(fieldnum(A, ItemId));

qbds = qbdsA.addDataSource(tablenum(B));
qbds.relations(true);
qbds.fetchMode(QueryFetchMode::One2One);

qbds = qbds.addDataSource(tablenum(C));
qbds.addLink(fieldnum(A, K), fieldnum(C, K), qbdsA.name())
qbds.fetchMode(QueryFetchMode::One2One);