SQL - 在两列中对字符进行分组和计数

Question

我有这张桌子：

|---------------------|------------------|------------------|
|      NAME           |     GENDER       |     JOB          |
|---------------------|------------------|------------------|
|      John           |     Male         |    Accountant    |
|---------------------|------------------|------------------|
|      Jane           |     Female       |    Accountant    |
|---------------------|------------------|------------------|
|      Stephen        |     Male         |    Sales         |
|---------------------|------------------|------------------|
|      James          |     Male         |    Accountant    |
|---------------------|------------------|------------------|
|      Hanna          |     Female       |    Sales         |
|---------------------|------------------|------------------|
|      Joe            |     Male         |    Sales         |
|---------------------|------------------|------------------|
|      Diana          |     Female       |    Sales         |
|---------------------|------------------|------------------|

...我想获得一张这样的表：

|---------------------|------------------|------------------|
|      JOB            |     MALE         |     FEMALE       |
|---------------------|------------------|------------------|
|      Accountant     |       2          |    1             |
|---------------------|------------------|------------------|
|      Sales          |       2          |    2             |
|---------------------|------------------|------------------|

所以我尝试了 group by，但我正在寻找更短更简单的查询

Answer 1

您正在寻找条件聚合：

select job,
       sum(case when gender = 'Male' then 1 else 0 end) as num_males,
       sum(case when gender = 'Female' then 1 else 0 end) as num_females
from t
group by job;

Answer 2

您可以为此使用PIVOT ：

设置

DECLARE @data as Table
(
    Name varchar(50) not null,
    Gender varchar(10) not null,
    Job varchar(10) not null
)
INSERT INTO @data (Name, Gender, Job)
VALUES ('John','Male','Accountant'),
('Jane','Female','Accountant'),
('Stephen','Male','Sales'),
('James','Male','Accountant'),
('Hanna','Female','Sales'),
('Joe','Male','Sales'),
('Diana','Female','Sales')

询问：

用你的表引用替换@data

SELECT Job, Male = SUM(Male), Female = SUM(Female)
FROM @data
PIVOT
(
    SUM ( Gender ) FOR
    Gender IN ( Male, Female )
) as pvtData
GROUP BY Job

Answer 3

你还没有标记你的数据库，但如果它是MySQL ，这将是“最短的”。 话虽如此，我建议使用显式 case 语句，而不是依靠语法怪癖来处理条件。

select job
      ,sum(gender = 'Male') num_males
      ,sum(gender = 'Female') num_females
from t
group by job;