orWhereExists method
Implementation
@override
QueryBuilder orWhereExists(QueryCallback callback, {bool not = false}) {
QueryBuilder subQuery = QueryBuilderImpl();
callback(subQuery);
String condition = "${not ? 'NOT EXISTS' : 'EXISTS'} (${subQuery.toSql()})";
_appendCondition(condition, isOr: true);
bindings.addAll(subQuery.getBindings());
return this;
}