从MySQL表的同一列中获取计数？

Question

我想对同一字段进行计数以获得不同的值，例如：

用户{user_id，性别}

性别显然可以是男性或女性：)

我想获得所有男性和女性的计数，即

COUNT(male)   COUNT(female)  
   4               16

但我很困惑，因为他们来自同样的gender coloumn感谢

Answer 1

尝试以下操作以获得明智的结果：

SELECT gender, COUNT(User_id) AS count
FROM User
GROUP BY gender;

输出：

| gender | count |
|--------|-------|
|      F |     4 |
|      M |     2 |

尝试以下操作以获得总计的行明智结果：

SELECT  (IFNull(gender,'Total')) AS gender,
COUNT(User_id) AS Count
FROM User
GROUP BY gender
WITH rollup;

输出：

| gender | Count |
|--------|-------|
|      F |     4 |
|      M |     2 |
|  Total |     6 |

尝试此操作以获得列明智的结果：

SELECT
  COUNT(CASE WHEN gender = 'M' THEN User_id END) AS males,
  COUNT(CASE WHEN gender = 'F' THEN User_id END) AS females,
  COUNT(*) AS Total
FROM User;

输出：

| males | females | Total |
|-------|---------|-------|
|     2 |       4 |     6 |

看到这个SQLFiddle