ZExp where = query.getWhere();
if(where instanceof ZExpression) {
parseZExpression((ZExpression) where, tablesNames);
}
// set
ZExpression set = query.getSet();
if(set!=null){
isUnion=true;
ZExp op = set.getOperand(0);
if(op instanceof ZQuery) getInvokedTables((ZQuery)op, tablesNames);
}
}