SQL Query tree-structured data

Today the SELECT statement found in Oracle can be used with the start with ... The Connect by prior clause implements a recursive query, and connect by is used in structured queries with the basic syntax:

Select ... from tablename start with Cond1
Connect by Cond2
where Cond3;

In short, a tree structure is stored in a table, for example, there are two fields in a list:
Id,parentid so by indicating who the parent of each record is, a tree structure can be formed.

Transferred from: http://blog.itpub.net/29564184/viewspace-1156956/

SQL Query tree-structured data