自引用表，单个查询中的父/子插入语句

Question

I have a self-referencing table, and I am wanting add both the parent and child examples in a single query. Is there a better way to do it then to break it down in a fashion similar to what I have below?

+---------------------+
|       example       |
+---------+-----------+
|   id    | parent_id |
+---------+-----------+
|    1    |           |
|    2    |     1     |
|    3    |     1     |
|    4    |     1     |
|    5    |           |
|    6    |     5     |
|    7    |     5     |
+---------+-----------+

DECLARE example_id INT;

INSERT INTO `example` (parent_id) VALUE("");

SET example_id = LAST_INSERT_ID();

INSERT INTO `example` (parent_id) VALUE (example_id);

Answer 1

If you are referring to tree structure with your question you should better check this article . If you would only have 1 level of children for parent then your way is possibly the simplest way around.

Answer 2

Your way of doing things looks OK.
In a real-world example you'll probably do an insert - select based on some criteria.

INSERT INTO example SELECT 
  null as id 
  ,e.id as parent_id
  ,10 as field1
  ,....
FROM example e WHERE e.somefield = 10 ORDER BY e.id DESC LIMIT 1;