计算不同的值 [英] Count distinct values

问题描述

我有一个数据集，询问客户例如他们有多少只宠物.有一种方法可以查询一个不同的值(1、2、3等)吗? 谢谢！

I have a data set asking a customer how many pets they have for example. Is there a way with one query I can count the distinct values (1,2,3, etc)? Thanks!

+----------+------+
| Customer | Pets |
+----------+------+
|       20 |    2 |
|       21 |    3 |
|       22 |    3 |
|       23 |    2 |
|       24 |    4 |
+----------+------+

我想要的是一个清单，上面写着:

What I want is a list saying:

• 2养了2只宠物
• 2养了3只宠物
• 1只养了4只宠物

推荐答案

您可以进行以下不同的计数:

You can do a distinct count as follows:

SELECT COUNT(DISTINCT column_name) FROM table_name;

在您对问题进行澄清和更新之后，我现在看到的是与我们最初想到的问题完全不同的问题. "DISTINCT"在SQL中具有特殊含义.如果我理解正确，那么您需要这样的东西:

Following your clarification and update to the question, I see now that it's quite a different question than we'd originally thought. "DISTINCT" has special meaning in SQL. If I understand correctly, you want something like this:

• 2位顾客养了1只宠物
• 3位顾客养了2只宠物
• 1位顾客养了3只宠物

现在您可能要使用子查询:

Now you're probably going to want to use a subquery:

select COUNT(*) column_name FROM (SELECT DISTINCT column_name);

让我知道这是否与您想要的不一样.

Let me know if this isn't quite what you're looking for.

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