SQL查找列中不同值的数量 [英] SQL to find the number of distinct values in a column

问题描述

我可以通过以下方式选择列中的所有不同值：

I can select all the distinct values in a column in the following ways:

• SELECT DISTINCT column_name FROM table_name;


• 从表名GROUP BY column_name中选择column_name;

• SELECT DISTINCT column_name FROM table_name;
• SELECT column_name FROM table_name GROUP BY column_name;

但是如何从该查询中获取行数？

But how do I get the row count from that query? Is a subquery required?

推荐答案

您可以在其中使用 DISTINCT 关键字 COUNT 聚合函数：

You can use the DISTINCT keyword within the COUNT aggregate function:

SELECT COUNT(DISTINCT column_name) AS some_alias FROM table_name

这将仅计算该列的不同值。

This will count only the distinct values for that column.

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