Question

我有一张如下表：

ID   Name   Department Gender
1    Crib     MA        MALE
2    Lucy     Bsc       FEMALE
3    Phil     Bcom      MALE
4    Ane      MA        FEMALE

我有1000行这样的记录。我想找到所有学生的性别（男性和女性）栏目的比例。

我需要一个查询来执行此操作。

Answer 1

SQL Fiddle

MySQL 5.5.32架构设置：

CREATE TABLE table1
    (`ID` int, `Name` varchar(4), `Department` varchar(4), `Gender` varchar(6))
;

INSERT INTO table1
    (`ID`, `Name`, `Department`, `Gender`)
VALUES
    (1, 'Crib', 'MA', 'MALE'),
    (2, 'Lucy', 'Bsc', 'FEMALE'),
    (3, 'Phil', 'Bcom', 'MALE'),
    (4, 'Ane', 'MA', 'FEMALE')
;

查询1 ：

SELECT sum(case when `Gender` = 'MALE' then 1 else 0 end)/count(*) as male_ratio,
       sum(case when `Gender` = 'FEMALE' then 1 else 0 end)/count(*) as female_ratio
FROM table1

<强> Results ：

| MALE_RATIO | FEMALE_RATIO |
|------------|--------------|
|        0.5 |          0.5 |

Answer 2

尝试这样的事情

select sum(case when gender = 'MALE' then 1 else 0 end) / count(*) * 100 as perc_male,
sum(case when gender = 'FEMALE' then 1 else 0 end) / count(*) * 100 as perc_female
from students

Answer 3

怎么样

select gender, count(*)
  from table
 group by gender

然后自己计算比率非常简单。

Answer 4

这应该给你实际的比例，并且应该在MySQL和SQL Server中很少或没有修改。您可能需要稍微修改一下cast语句 - 我的MySQL已经生锈了，我认为它可能会略有不同。

SELECT 
    (CAST((SELECT COUNT(*) FROM tblName WHERE Gender='MALE') AS FLOAT) / 
     CAST((SELECT COUNT(*) FROM tblName WHERE Gender='FEMALE') AS FLOAT)) 
    AS ratioMaleFemale;

Answer 5

你非常接近：

select (select count(*) 
          from table where gender='MALE' )/count(*)*100 as percentage_male,
       (select count(*) 
          from table where gender='FEMALE' )/count(*)*100 as percentage_female 
from table;

如何使用sql查询计算比率？

5 个答案: