在 SQL 中分组之前组合结果

Question

我想根据客户的头衔（先生、夫人等）计算出客户的男女比例

为此，我需要将 Miss/Mrs/Ms 的结果合并到一个“女性”字段中。

下面的查询获取每个标题的总数，但我想我需要一个子查询来返回组合的女性形象。

任何帮助将不胜感激。

Query:
SELECT c.Title, COUNT(*) as Count
FROM
   Customers c
GROUP BY Title
ORDER By [Count] DESC

Answer:
Mr  1903
Miss    864
Mrs 488
Ms  108

Answer 1

你可以这样做

SELECT 
  [Gender] = CASE [Title] WHEN 'Mr' THEN 'M' ELSE 'F' END, 
  COUNT(*) as Count
FROM
   Customers c
GROUP BY 
  CASE [Title] WHEN 'Mr' THEN 'M' ELSE 'F' END
ORDER By 
  [Count] DESC

http://sqlfiddle.com/#!3/05c74/4的演示

Answer 2

您可以使用 CASE 为 Titles 投影新组：

SELECT SUM(CASE WHEN Title IN ('Mr') THEN 1 ELSE 0 END) AS Male,
       SUM(CASE WHEN Title IN ('Miss', 'Ms', 'Mrs') THEN 1 ELSE 0 END) AS Female
FROM
   Customers c;

Answer 3

试试这个：

SELECT (CASE WHEN c.Title = 'Mr' THEN 'Male' 
             WHEN c.Title IN ('Mrs', 'Miss', 'Ms') THEN 'Female' 
             ELSE 'NA' 
        END) AS title, 
        COUNT(1) AS PeopleCount
FROM Customers c
GROUP BY (CASE WHEN c.Title = 'Mr' THEN 'Male' 
              WHEN c.Title IN ('Mrs', 'Miss', 'Ms') THEN 'Female' 
              ELSE 'NA' 
         END)
ORDER By PeopleCount DESC;