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SQL COUNT, SUM, AVG

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The SQL COUNT(), SUM() and AVG() Functions

These are three of the most common aggregate functions in SQL.

COUNT() Function

The COUNT() function returns the number of rows that matches a specified criterion.

COUNT() Syntax

SELECT COUNT(column_name)
FROM table_name
WHERE condition;

COUNT(*) returns the total number of records in a table. COUNT(column_name) returns the number of non-NULL values in that column.

SUM() Function

The SUM() function returns the total sum of a numeric column.

SUM() Syntax

SELECT SUM(column_name)
FROM table_name
WHERE condition;

AVG() Function

The AVG() function returns the average value of a numeric column.

AVG() Syntax

SELECT AVG(column_name)
FROM table_name
WHERE condition;

Demo Database

Below is a selection from the Orders table:

Orders Table:

OrderID CustomerID OrderDate
10308 2 1996-09-18
10309 37 1996-09-19
10310 77 1996-09-20

Example 1: Using COUNT()

The following SQL statement finds the total number of orders in the Orders table.

COUNT() Example

SELECT COUNT(OrderID) FROM Orders;

Example 2: Using SUM()

The following SQL statement finds the sum of the "CustomerID" fields for all orders.

SUM() Example

SELECT SUM(CustomerID) FROM Orders;

Example 3: Using AVG()

The following SQL statement finds the average CustomerID for all orders.

AVG() Example

SELECT AVG(CustomerID) FROM Orders;
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