GROUP BY First_Name 但显示对应 Last_Name SQL 的 COUNT答案

【问题标题】：GROUP BY First_Name but show COUNT of the corresponding Last_Name SQLGROUP BY First_Name 但显示对应 Last_Name SQL 的 COUNT
【发布时间】：2014-07-25 15:26:14
【问题描述】：

我有一个 SQL 语句，它将按 First_Name 计算出现次数和分组，但出于其他目的，我需要知道有多少家庭成员是客户以及使用相同的姓氏的 COUNT。这是我写的代码。

SELECT a.Last_Name, a.First_Name,
SUM(CASE WHEN b.ITM = 'P_10' THEN 1 ELSE 0 END) AS P_10_COUNT
FROM CUST_PROFILE
INNER JOIN ORDER b
ON a.ID = b.ID
GROUP BY a.First_Name, a.Last_Name;

我对如何编写代码有一个粗略的想法（也许），见下文....

SELECT a.Last_Name, a.First_Name,
SUM(CASE WHEN b.ITM = 'P_10' THEN 1 ELSE 0 END) AS P_10_COUNT,
COUNT(c.Name_Count)
FROM CUST_PROFILE
INNER JOIN ORDER b
ON a.ID = b.ID
LEFT JOIN (select Last_Name, count(DISTINCT First_Name) Name_Count
from CUST_PROFILE
GROUP BY Last_Name) c
GROUP BY a.First_Name, a.Last_Name;

【问题讨论】：

标签： sql count distinct

【解决方案1】：

看起来一切正常，您只需要JOIN您的子选择

SELECT a.Last_Name, a.First_Name,
SUM(CASE WHEN b.ITM = 'P_10' THEN 1 ELSE 0 END) AS P_10_COUNT,
COUNT(c.Name_Count)
FROM CUST_PROFILE
INNER JOIN ORDER b
ON a.ID = b.ID
LEFT JOIN (select Last_Name, count(DISTINCT First_Name) Name_Count
from CUST_PROFILE
GROUP BY Last_Name) c ON c.Last_Name = a.Last_Name
GROUP BY a.First_Name, a.Last_Name;

【讨论】：

这个语法是我一直在寻找的，但如果他们也购买了 p_10，它只计算其他名字，有没有办法在计算家庭成员时排除它。

【解决方案2】：

SELECT a.Last_Name, a.First_Name,
SUM(CASE WHEN b.ITM = 'P_10' THEN 1 ELSE 0 END) AS P_10_COUNT,
c.Name_Count
FROM CUST_PROFILE
INNER JOIN ORDER b
ON a.ID = b.ID
LEFT JOIN (select Last_Name, count(DISTINCT First_Name) Name_Count
from CUST_PROFILE
GROUP BY Last_Name) c ON c.Last_Name = a.Last_Name
GROUP BY a.First_Name, a.Last_Name,c.Name_Count;

【讨论】：