Select count (distinct)

I want to count the number of fields a in a table. Because field a has repeated records, I want to exclude repeated records. The SQL statement is:

Select count (distinct)

 

Link: http://www.w3school.com.cn/ SQL/SQL _func_count_distinct.asp

 

Definition and usage

The distinct and count keywords can be used together to calculate the number of non-repeated results.

Syntax

SELECT COUNT(DISTINCT column(s)) FROM table

 

Example

Note: The following example applies only to Oracle and Microsoft SQL Server, and cannot be used for Microsoft Access.

"Orders" table:

Company	Ordernumber
IBM	3532
W3school	2356
Apple	4698
W3school	6953

Example 1

SELECT COUNT(Company) FROM Orders

Result:

4

Example 2

SELECT COUNT(DISTINCT Company) FROM Orders

Result:

3

 

Select count (distinct)