Note: The following example works with ORACLE and Microsoft SQL server but not with Microsoft Access.
注意：下面的举例适用于ORCLE和MSSQL，不能在Access中使用。

The keyword DISTINCT and COUNT can be used together to count the number of distinct results.

语法

SELECT COUNT(DISTINCT column(s)) FROM table

举例

With this "Orders" Table:
用的是这张"Orders"表:

举例

SELECT COUNT(Company) FROM Orders

结果:

4

举例

SELECT COUNT(DISTINCT Company) FROM Orders

结果:

3

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