MySQL为列中的每个唯一项选择计数行

用一个例子来解释是最容易的。假设我有一张有3列的桌子——父亲、他们的后代和他们孩子的性别。结果表将列出父亲的子女数量以及男女比例

这是表格：

Father   Child    Sex
-----------------------
alpha    name1    m
alpha    name2    f
alpha    name3    m
alpha    name4    f
alpha    name5    f
beta     name6    m
beta     name7    m
charlie  name8    f
charlie  name9    m

预期结果：

Father   num   m    f
-----------------------
alpha    5     2    3
beta     2     2    0
charlie  2     1    1

num = number of children
m = male, f = female

当我使用count时，它会给我所有父亲的孩子总数，我不知道如何将结果分为男性和女性。 有什么想法吗？

类似这样的想法：

select distinc t.Father, 
(select count(1) from table t1 where t1.Father = t.Father) as num,
(select count(1) from table t1 where t1.Father = t.Father and Sex = 'm') as m,
(select count(1) from table t1 where t1.Father = t.Father and Sex = 'f') as f
from table t;

大概是这样的：

select distinc t.Father, 
(select count(1) from table t1 where t1.Father = t.Father) as num,
(select count(1) from table t1 where t1.Father = t.Father and Sex = 'm') as m,
(select count(1) from table t1 where t1.Father = t.Father and Sex = 'f') as f
from table t;

---

诀窍是在布尔变量周围使用

SUM（）

SELECT Father, COUNT(Child) as num, SUM(Sex='m') as m, SUM(Sex='f') as f
FROM table
GROUP BY Father;

---

诀窍是在布尔变量周围使用

SUM（）

SELECT Father, COUNT(Child) as num, SUM(Sex='m') as m, SUM(Sex='f') as f
FROM table
GROUP BY Father;

尝试：

尝试：

---

显示返回错误计数的sql语句显示返回错误计数的sql语句counts@RobertRozas多亏了正确的拼写…但还没有测试。格里耶什和我回到了过去。他是SQL公司的人。我只是为了好玩。@dredness谢谢：）我在想@GrijeshChauhan-哦，是的，伙计！发件人：）德鲁内斯的好人xD@RobertRozas多亏了正确的拼写…但还没有测试。格里耶什和我回到了过去。他是SQL公司的人。我只是为了好玩。@dredness谢谢：）我在想@GrijeshChauhan-哦，是的，伙计！发件人：）好人@德鲁内斯xD