Question

我有两张桌子：

客户

id      name
1       John
2       Kevin

customer_property

id      customer_id    code              value       
1       1              main_course                   
2       1              main_course                   
3       1              drink                         
4       1              drink                         
5       1              cash              100

我想要计算每个客户订购的课程和饮料。我可以通过这个问题来计算饮料：

SELECT
  c.name,
  COUNT(DISTINCT cp.id) AS drinks_count
FROM customer AS c
  JOIN customer_property AS cp ON c.id=cp.customer_id
WHERE cp.code="drink"
  GROUP BY cp.id

工作正常。我的问题 - 可以在同一个查询中计算课程吗？

Answer 1

您可以为此使用条件求和，并按cp.id进行分组将为您提供该表中的许多行，您可以将其作为c.name

SELECT
  c.name,
  sum(cp.code="drink") AS drinks_count,
  sum(cp.code="main_course") AS main_course_count,
FROM customer AS c
  JOIN customer_property AS cp ON c.id=cp.customer_id
  GROUP BY c.name

Answer 2

你可以试试这个：

SELECT
c.name,
cp.code,
COUNT(DISTINCT cp.id) AS drink_or_course_count
FROM customer AS c
JOIN customer_property AS cp ON c.id=cp.customer_id
WHERE cp.code="drink" or cp.code="main_course"
GROUP BY cp.id,cp.code

按人员ID分类 AND 代码将按代码拆分计数。结果将类似于

 Name  Code  drink_or_course_count
 John  drink  5
 john  main_course 3

在mysql中计算分组值

2 个答案: