mysql - sql How to query the third-level subset based on the parent id?

Question

Now there is a need to query the third-level subset based on fid
A database table has three fields (id, name, fid)
id name fid
1 01 0
2 02 1
3 03 2
4 04 3
5 05 3
6 06 4
7 07 6
.............

Now how to query the content of the next three levels based on id
For example, if you check the lower three-level subset with id=3, the result is as follows. Is it best to display the level level?
id name fid (level)
4 04 3 1
5 05 3 1
6 06 4 2
7 07 6 3
How do you write this kind of SQL

Answer 1

Let’s query it recursively

Answer 2

Add a field level to the table and load all the data into the memory. Calculate the level and make corrections to the database. All future queries will be much easier.