sql--aggregate function (Aggregate functions): Avg,count,first,last,max,min,sum

sql--aggregate function (Aggregate functions): Avg,count,first,last,max,min,sum

avg () function Definition and Usage

The AVG function returns the average of a numeric column. NULL values are not included in the calculation.

SQL AVG () syntax

SELECT AVG (column_name) from table_name

SQL AVG () instance

We have the following "Orders" table:

o_id	OrderDate	Orderprice	Customer
1	2008/12/29	1000	Bush
2	2008/11/23	1600	Carter
3	2008/10/05	700	Bush
4	2008/09/28	300	Bush
5	2008/08/06	2000	Adams
6	2008/07/21	100	Carter

Example 1

Now, we want to calculate the average of the "Orderprice" field.

We use the following SQL statement:

SELECT AVG (Orderprice) as Orderaverage from Orders

The result set looks like this:

Orderaverage
950

Example 2

Now, we want to find customers with Orderprice values above the Orderprice average.

We use the following SQL statement:

Select Customer from Orderswhere orderprice> (select AVG (orderprice) from Orders)

The result set looks like this:

Customer
Bush
Carter
Adams

count () function

The count () function returns the number of rows that match the specified criteria.

SQL count () syntax SQL COUNT (column_name) syntax

The count (column_name) function returns the number of values for the specified column (NULL does not count in):

SELECT COUNT (column_name) from table_name

SQL COUNT (*) syntax

The count (*) function returns the number of records in the table:

SELECT COUNT (*) from table_name

SQL COUNT (DISTINCT column_name) syntax

The COUNT (DISTINCT column_name) function returns the number of different values for the specified column:

SELECT COUNT (DISTINCT column_name) from table_name

Note: COUNT (DISTINCT) applies to ORACLE and Microsoft SQL Server, but not to Microsoft Access.

SQL COUNT (column_name) instance

We have the following "Orders" table:

o_id	OrderDate	Orderprice	Customer
1	2008/12/29	1000	Bush
2	2008/11/23	1600	Carter
3	2008/10/05	700	Bush
4	2008/09/28	300	Bush
5	2008/08/06	2000	Adams
6	2008/07/21	100	Carter

Now, we want to calculate the number of orders for the customer "Carter".

We use the following SQL statement:

SELECT COUNT (Customer) as Customernilsen from Orderswhere customer= ' Carter '

The result of the above SQL statement is 2 because there are 2 orders for customer Carter:

Customernilsen
2

SQL COUNT (*) instance

If we omit the WHERE clause, such as this:

SELECT COUNT (*) as numberoforders from Orders

The result set looks like this:

Numberoforders
6

This is the total number of rows in the table.

SQL COUNT (DISTINCT column_name) instance

Now, we want to calculate the number of different customers in the Orders table.

We use the following SQL statement:

SELECT COUNT (DISTINCT Customer) as Numberofcustomers from Orders

The result set looks like this:

Numberofcustomers
3

This is the number of different customers (Bush, Carter, and Adams) in the Orders table.

First () function

The first () function returns the value of the number one record in the specified field.

Tip: You can use the order BY statement to sort records.

SQL First () syntax

SELECT First (column_name) from table_name

SQL First () instance

We have the following "Orders" table:

o_id	OrderDate	Orderprice	Customer
1	2008/12/29	1000	Bush
2	2008/11/23	1600	Carter
3	2008/10/05	700	Bush
4	2008/09/28	300	Bush
5	2008/08/06	2000	Adams
6	2008/07/21	100	Carter

Now, we want to find the first value of the "Orderprice" column.

We use the following SQL statement:

SELECT First (Orderprice) as Firstorderprice from Orders

The result set looks like this:

Firstorderprice
1000

Last () function

The last () function returns the value of the final record in the specified field.

Tip: You can use the order BY statement to sort records.

SQL last () syntax

SELECT last (column_name) from table_name

SQL last () instance

We have the following "Orders" table:

o_id	OrderDate	Orderprice	Customer
1	2008/12/29	1000	Bush
2	2008/11/23	1600	Carter
3	2008/10/05	700	Bush
4	2008/09/28	300	Bush
5	2008/08/06	2000	Adams
6	2008/07/21	100	Carter

Now, we want to find the last value of the "Orderprice" column.

We use the following SQL statement:

SELECT last (Orderprice) as Lastorderprice from Orders

The result set looks like this:

Lastorderprice
100

max () function

The Max function returns the maximum value in a column. NULL values are not included in the calculation.

SQL MAX () syntax

SELECT MAX (column_name) from table_name

Note: MIN and MAX can also be used for text columns to get the highest or lowest values in alphabetical order.

SQL MAX () instance

We have the following "Orders" table:

o_id	OrderDate	Orderprice	Customer
1	2008/12/29	1000	Bush
2	2008/11/23	1600	Carter
3	2008/10/05	700	Bush
4	2008/09/28	300	Bush
5	2008/08/06	2000	Adams
6	2008/07/21	100	Carter

Now, we want to find the maximum value for the "Orderprice" column.

We use the following SQL statement:

SELECT MAX (Orderprice) as Largestorderprice from Orders

The result set looks like this:

Largestorderprice
2000

min () function

The Min function returns the minimum value in a column. NULL values are not included in the calculation.

SQL MIN () syntax

SELECT MIN (column_name) from table_name

Note: MIN and MAX can also be used for text columns to get the highest or lowest values in alphabetical order.

SQL MIN () instance

We have the following "Orders" table:

o_id	OrderDate	Orderprice	Customer
1	2008/12/29	1000	Bush
2	2008/11/23	1600	Carter
3	2008/10/05	700	Bush
4	2008/09/28	300	Bush
5	2008/08/06	2000	Adams
6	2008/07/21	100	Carter

Now, we want to find the minimum value for the "Orderprice" column.

We use the following SQL statement:

SELECT MIN (Orderprice) as Smallestorderprice from Orders

The result set looks like this:

Smallestorderprice
100

sum () function

The SUM function returns the total number of numeric columns (total).

SQL SUM () syntax

SELECT SUM (column_name) from table_name

SQL SUM () instance

We have the following "Orders" table:

o_id	OrderDate	Orderprice	Customer
1	2008/12/29	1000	Bush
2	2008/11/23	1600	Carter
3	2008/10/05	700	Bush
4	2008/09/28	300	Bush
5	2008/08/06	2000	Adams
6	2008/07/21	100	Carter

Now, we want to find the total number of "Orderprice" fields.

We use the following SQL statement:

SELECT SUM (Orderprice) as OrderTotal from Orders

The result set looks like this:

OrderTotal
5700

sql--aggregate function (Aggregate functions): Avg,count,first,last,max,min,sum