@NonNull
    public String getSql() {
        return constructSqlInternal(CollectionStream.of(columns).map(c -> getMainTableId() + "." + c).toJoinedString(", "), true, true);
    }
Returns SQL as currently defined by this builder.
<br />
Method does not change the classes state. It may return incomplete SQL e.g. if not all where's are closed yet
main/src/main/java/cgeo/geocaching/storage/SqlBuilder.java