Mysql查询中的多级层次结构

Question

我正在寻找多级递归查询，我试图找到用户组

customer_hierarchy表

customer_code | parent_code |
001           | 002         |
002           | 003         |
003           | 004         |
004           | 006         |
005           | 007         |

CUSTOMER_TABLE

--------------------------------
customer_code | customer_group |
001           | G1             |
002           | G2             |
003           | G3             |
004           | G4             |
001           | G5             |

预期结果

--------------------------------
customer_code | customer_group |
001           | G1,G2,G3,G4    |
002           | G2,G3,G4       |
003           | G3,G4          |
004           | G2             |

我尝试使用以下查询，但没有正常工作

SELECT GROUP_CONCAT(lv SEPARATOR ',') FROM (
SELECT @pv:=(SELECT GROUP_CONCAT(customer_code SEPARATOR ',') FROM customer_hierarchy 
WHERE FIND_IN_SET(parent_customer, @pv)) AS lv FROM customer_hierarchy 
JOIN
(SELECT @pv:=0000000027) tmp
) a;