Question

我有一个表“ table1 ”，其中有一个“ parents_list ”。现在，我将只获得每行状态最高的一个父级，并从该父级中获得下一个父级（2个或以上）。我写的查询就是这个。但是它只返回“ parent_name＆parent_name_2” NULL ：

  storageClassName: manual

表格：

SELECT t1.id, parents.name as parent_name, parents2.name as parent_name_2
from table1 as t1
LEFT JOIN table1 as parents ON parents.id = (
  SELECT id from table1 WHERE parents_list IN (SUBSTR(REPLACE(t1.parents_list,';', ','),1 , CHAR_LENGTH(t1.parents_list) - 1)) AND status > 1 ORDER BY status DESC LIMIT 1
)
LEFT JOIN table1 as parents2 ON parents2.id = (
  SELECT id from table1 WHERE parents_list IN (SUBSTR(REPLACE(parents2.parents_list,';', ','),2 , CHAR_LENGTH(parents2.parents_list) - 2)) AND status > 1 ORDER BY status DESC LIMIT 1
)
WHERE t1.date BETWEEN '2018-05-15' AND '2018-06-20'

“ ID：5”行的结果应为：

| id | name | date | parents_list | status | 
| ---: | --- | --- | --- | ---: | 
| 1 | test 1 | 2018-05-18 |  | 3 | 
| 2 | test 2 | 2018-05-25 | ;1; | 3 | 
| 3 | test 3 | 2018-05-23 | ;5;1;4; | 8 | 
| 4 | test 4 | 2018-05-30 | ;1;3; | 5 | 
| 5 | test 5 | 2018-06-05 | ;2;4;3; | 6 |

但当前结果是：

| id | parent_name| parent_name_2 |
| 5 | test 3 | test 1 |

我如何才能使该查询生效，或者有更好的方法呢？

P.S。我无法更改表格设计：（

MySQL-LEFT JOIN从同一表获取父项

0 个答案: