Question

我正在使用标准的婴儿名字数据集。我有一栏列出姓名，频率和性别。我想在一个查询中同时获得男性和女性的姓氏。我可以通过单个查询轻松地做到这一点，但是如何只用一个查询呢？

SELECT names,sex,MAX(frequency) from babynames WHERE year=1973 and sex='M';

我将如何扩展该名称，使之成为每年M和F最受欢迎的名字？

Answer 1

很容易获得一种性别的最常用名字：

SELECT names, sex, frequency from babynames WHERE year = 1973 and sex = 'M'
ORDER BY frequency DESC
LIMIT 1

要获得两个名称，请在UNION ALL中输入“ F”性别。

类似的东西：

select * from
(
SELECT names, sex, frequency from babynames WHERE year = 1973 and sex = 'F'
ORDER BY frequency DESC
LIMIT 1
)
UNION ALL
(
SELECT names, sex, frequency from babynames WHERE year = 1973 and sex = 'M'
ORDER BY frequency DESC
LIMIT 1
)

Answer 2

一种方法使用相关的子查询：

select bn.*
from babynames bn
where bn.year = 1973 and
      bn.frequency = (select max(bn2.frequency)
                      from babynames bn2
                      where bn2.sex = bn.sex and bn2.year = bn.year
                     );

使用SQL查询如何获取两个单独的MAX值？

2 个答案: