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

Posted on 2014-10-21
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Last Modified: 2014-10-21
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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Question by:roosterup
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Accepted Solution

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Jim Horn earned 500 total points
ID: 40394469
SELECT COUNT(DISTINCT CustomerNumber)
FROM YourTable
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Expert Comment

by:Jim Horn
ID: 40394509
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.
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Expert Comment

by:Lieven Embrechts
ID: 40394510
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.

Example:
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:
Example:
SELECT count(*)
FROM
(SELECT DISTINCT CustNbr FROM CustTable1)
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Expert Comment

by:Lieven Embrechts
ID: 40394633
ok, thanks
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