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SQL Anywhere 11.0.1 » SQL Anywhere Server - SQL Usage » Querying and Modifying Data » Summarizing, grouping, and sorting query results » Summarizing query results using aggregate functions

 

Aggregate functions and NULL

Any NULLS in the column on which the aggregate function is operating are ignored for the purposes of the function except COUNT(*), which includes them. If all the values in a column are NULL, COUNT(column_name) returns 0.

If no rows meet the conditions specified in the WHERE clause, COUNT returns a value of 0. The other functions all return NULL. Here are examples:

SELECT COUNT( DISTINCT Name )
   FROM Products
   WHERE UnitPrice > 50;
COUNT(DISTINCT Name)
0
SELECT AVG( UnitPrice )
   FROM Products
   WHERE UnitPrice > 50;
AVG(Products.UnitPrice)
( NULL )