使用 GROUP BY - MYSQL 根据行级项目获取列答案

【问题标题】：Get column based on line level items using GROUP BY - MYSQL使用 GROUP BY - MYSQL 根据行级项目获取列
【发布时间】：2022-09-23 12:52:59
【问题描述】：

MYSQL TABLE

上下文：对于上表，我想在组级别创建一个带有 order_no 和 Manufacture 列的视图“VIEW_A”。

where Manufacture  = A if line level items have `manf` = A or \"\".
where Manufacture  = B if line level items have `manf` = B
where Manufacture  = Mixed if line level items have `manf` A and B.

How can I solve the issue?

Tips for asking a good Structured Query Language (SQL) question 和 Please do not upload images of code/data/errors when asking a question.

标签： mysql phpmyadmin

【解决方案1】：

您可以计算订单项“A”和订单项“B”，然后将这些数字与每个订单的订单项总数进行比较：

SELECT order_no, 
       CASE WHEN sum(CASE WHEN `manf` = 'A' THEN 1 END) = count(*) THEN 'A'
            WHEN sum(CASE WHEN `manf` = 'B' THEN 1 END) = count(*) THEN 'B'
            ELSE 'Mixed' END Manufacture
  FROM mytable
 GROUP BY order_no;

【讨论】：