Total the number of unique customer numbers in a table with an sql statement

I have a table with a customer number field. The customer number can be in the table multiple times.  I need to total of the number of unique customer numbers in the file. In other words, how many customers do I have?

How can I do this in sql?
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Jim HornSQL Server Data DudeCommented:
FROM YourTable

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Jim HornSQL Server Data DudeCommented:
Thanks for the grade.  I have an article out there on SQL Server GROUP BY Solutions, and just noticed that COUNT(DISTINCT) is not on it, so I'll have to add it.  Thanks.
Lieven EmbrechtsSenior IT ConsultantCommented:
The COUNT(DISTINCT column_name) function returns the number of distinct values of the specified column:
eg. : SELECT COUNT(DISTINCT column_name) FROM table_name;
Note: COUNT(DISTINCT) works with ORACLE and Microsoft SQL Server, but not with Microsoft Access.

The following SQL statement counts the number of unique customers in the "Orders" table:
SELECT COUNT(DISTINCT CustomerID) AS NumberOfCustomers FROM Orders;

When count(distinct) is not supported (as in access), you can split the count and distinct in a sub-query:
SELECT count(*)
Lieven EmbrechtsSenior IT ConsultantCommented:
ok, thanks
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