mysql 怎么实现sql的with递归

概念说不一定理解，给你一个例子你自己参悟。 SELECT TEACHER FROM C AS X WHERE UNIQUE(SELECT TEACHER FROM C AS Y WHERE Y.TEACHER=X.TEACHER)

with a as

(select * from table1 where parentid=0

union all

select b.* from a,table1 b where a.id=b.parentid)

select * from a

用with as 来实现递归

单表自身关联查询，关联条件就是父节点pcode和code相等，查询字段包含pcode和sorce，将查询结果作为新表按pcode分组，用group by，查询字段是count记录数，这样就获取pcode的节点值，这是整体思路

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