Question

我需要一个如下所示的要求，任何人都可以请求帮助我，具体取决于parent_id和id

 id | category_name | parent_id 

 1    Electronics         0        

 2    computer            1

 3    ram                 2

 4    Fashion             0

 5    tshirt              4

 6     round neck         5

我需要如下要求

category name     |      sub category     |      sub sub category  | 

Electronics                NA                        NA

Electronics                computer                  NA

Electronics                computer                  ram

Fashion                    NA                        NA

Fashion                    tshirt                    NA

Fashion                    tshirt                   round neck

请帮助

Answer 1

经过几个小时的痛苦和痛苦，我得到了以下疑问。请注意，上面给出的评论链接对我没有任何帮助。

SELECT t.* FROM
(
    SELECT COALESCE(c3.category_name, c2.category_name, c1.category_name, 'NA') AS `category name`,
        CASE WHEN c3.category_name IS NOT NULL
            THEN c2.category_name
            ELSE
                CASE WHEN c2.category_name IS NOT NULL
                    THEN c1.category_name
                    ELSE 'NA'
                END 
        END AS `sub category`,
        CASE WHEN c3.category_name IS NOT NULL
            THEN c1.category_name
            ELSE 'NA'
        END AS `sub sub category`
    FROM category c1 LEFT JOIN category c2
        ON c1.parent_id = c2.id
    LEFT JOIN category c3
        ON c2.parent_id = c3.id ) t
ORDER BY t.`category name`,
    CASE WHEN t.`sub category` = 'NA' THEN NULL ELSE t.`sub category` END,
    CASE WHEN t.`sub sub category` = 'NA' THEN NULL ELSE t.`sub sub category` END

请按照以下链接查看正在运行的演示：

SQLFiddle

获取结构化数据mysql

1 个答案: