MySql8 WITH RECURSIVE recursive query parent-child collection method

Calculate the cumulative result from 1 to 100.
WITH RECURSIVE t(n) AS ( //t is our result table, n is the field, you can specify only one field to indicate that no field is specified VALUES (1) //The start of recursion, at this point it can be understood that the t table field n has only one record 1
 UNION ALL
  SELECT n+1 FROM t WHERE n < 100   
  /*The result here is 2. At this time, the field n of the t table has two records, 1 and 2 respectively.
  * 3
  * ...
  * 100
  */													  
)
SELECT sum(n) FROM t; //Sum field n

WITH RECURSIVE temp AS ( // Name the result table temp
	SELECT * FROM resource r WHERE r.name = '张三' //Query the record of the parent id. At this time, this record already exists in the temp table, as shown in Figure 1-1
	UNION ALL
	/*At this time, please note that the following sql is the last two records in the expected result (excluding the first one)
	*Note the condition after where, we use the id of the only record in the temp table to associate the pid in the resource table
	*The second record id of temp will be matched only when the first record of temp does not match the pid in the resource table */
	SELECT r.* FROM resource r,temp t WHERE t.id = r.pid
)select * from temp 

WITH recursive temp AS (
	SELECT * FROM resource r WHERE r.name = '张三孙子'
	UNION ALL
	//It is known that it is a subset, so we need to match the resource id through the temp pid
	SELECT r.* FROM resource r,temp t WHERE t.pid = r.id
)select * from temp