query for blog FIREBASE + REACTJS

Question

I have been trying to do a Firebase query for my blog for many days. I have this data structure.

[{ "-M5ivrqL4XMxI3dYokP0" : { -> ID group "title" : "group stackoverflow", "members" : { "-M88aIjP1ENue0GChAE1" : { "acepted" : "1", "comment" : "lorem ipsum", "createdAt" : "24-05-2020 22:11", "idUser" : "W1fQvOYOATXIiNEj0hG07339sIe2" }, "-M95m_Tv1XnD0KlAQeXx" : { "acepted" : "1", "comment" : "lorem ipsum", "createdAt" : "05-06-2020 19:21", "idUser" : "6xo3Y3yb2KeQvjW8Csxnbcqd2xH2" }, } } }]

What I'm looking for is to bring the group and all the users with name and thumbnail to show them in an avatar component. Something like the inner join in sql, but in firebase i have not managed to get it. thanks.

Answer 1

Firebase doesn't have an equivalent of SQL join statements. If you want to get data for two different entities (blog/members and user in your case), you have two options:

1. Read the data for each member after you get the relevant blog.
2. Duplicate the relevant data for each user into each blog they're a member of.

Neither of these is pertinently better than the other, although the second is more common under folks that optimize for read throughput, while the former is more common under folks that are newer to NoSQL data modeling.

Some recommended reading to get to grips with this:

• NoSQL data modeling.
• The video series Firebase for SQL developers.
• Getting to know Cloud Firestore, which is about Firestore but covers many principles that equally apply to the Realtime Database.
• Join two nodes in Firebase
• Speed up fetching posts for my social network app by using query instead of observing a single event repeatedly, which explains why client-side joins are not as slow as you may think.