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.
And 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 |