The goal of this type of query is to find the child documents that are associated with a parent type and meet the criteria of the parent. It can be read as which children have a parent that meets the criteria? Let's take an example to find child documents that have the cf_etf parent relation and the parent's symbol is ACWF. As shown in the following screenshot, all 10 records meet these criteria:

So far, we have introduced different approaches for data modeling and we will give a brief practical overview in the next section.