SQL SELECT COUNT, SUM, and AVG
How are aggregate values calculated in SQL?
- SELECT COUNT returns a count of the number of data values.
- SELECT SUM returns the sum of the data values.
- SELECT AVG returns the average of the data values.
The SQL SELECT COUNT, SUM, and AVG syntax
The general COUNT syntax is:
SELECT COUNT(column-name) FROM table-name
The general SUM syntax is:
SELECT SUM(column-name) FROM table-name
The general AVG syntax is:
SELECT AVG(column-name) FROM table-name
| CUSTOMER |
|---|
| Id |
| FirstName |
| LastName |
| City |
| Country |
| Phone |
SQL SELECT COUNT, SUM,
and AVG Examples
Problem: Find the total number of customers.
SELECT COUNT(Id) FROM Customer
Result:
| Count |
|---|
| 91 |
| ORDER |
|---|
| Id |
| OrderDate |
| OrderNumber |
| CustomerId |
| TotalAmount |
Problem: Compute the total amount sold in 2013.
SELECT SUM(TotalAmount) FROM [Order] WHERE YEAR(OrderDate) = 2013
Result:
| Sum |
|---|
| 658388.75 |
| ORDER |
|---|
| Id |
| OrderDate |
| OrderNumber |
| CustomerId |
| TotalAmount |
Problem: Compute the average size of all orders.
SELECT AVG(TotalAmount) FROM [Order]
Result:
| Average |
|---|
| 1631.877819 |
in Austin, Texas