SQL Aggregate Functions

• SQL aggregation function is used to perform the calculations on multiple rows of a single column of a table. It returns a single value.
• It is also used to summarize the data.

Types of SQL Aggregation Function

1. COUNT FUNCTION

• COUNT function is used to Count the number of rows in a database table. It can work on both numeric and non-numeric data types.
• COUNT function uses the COUNT(*) that returns the count of all the rows in a specified table. COUNT(*) considers duplicate and Null.

Syntax

COUNT(*)
or
COUNT( [ALL|DISTINCT] expression )

Sample table:

PRODUCT_MAST

Example: COUNT()

SELECT COUNT(*)
FROM PRODUCT_MAST;

Output:

10

Example: COUNT with WHERE

SELECT COUNT(*)
FROM PRODUCT_MAST;
WHERE RATE>=20;

Output:

7

Example: COUNT() with DISTINCT

SELECT COUNT(DISTINCT COMPANY)
FROM PRODUCT_MAST;  

Output:

3

Example: COUNT() with GROUP BY

SELECT COMPANY, COUNT(*)
FROM PRODUCT_MAST
GROUP BY COMPANY;

Output:

Com1    5
Com2    3
Com3    2

Example: COUNT() with HAVING

SELECT COMPANY, COUNT(*)
FROM PRODUCT_MAST
GROUP BY COMPANY
HAVING COUNT(*)>2;

Output:

Com1    5
Com2    3

2. SUM Function

Sum function is used to calculate the sum of all selected columns. It works on numeric fields only.

Syntax

SUM()
or
SUM( [ALL|DISTINCT] expression )

Example: SUM()

SELECT SUM(COST)
FROM PRODUCT_MAST;

Output:

670

Example: SUM() with WHERE

SELECT SUM(COST)
FROM PRODUCT_MAST
WHERE QTY>3;

Output:

320

Example: SUM() with GROUP BY

SELECT SUM(COST)
FROM PRODUCT_MAST
WHERE QTY>3
GROUP BY COMPANY;

Output:

Com1    150
Com2    170

Example: SUM() with HAVING

SELECT COMPANY, SUM(COST)
FROM PRODUCT_MAST
GROUP BY COMPANY
HAVING SUM(COST)>=170;

Output:

Com1    335
Com3    170

3. AVG function

The AVG function is used to calculate the average value of the numeric type. AVG function returns the average of all non-Null values.

Syntax

AVG()
or
AVG( [ALL|DISTINCT] expression )

Example:

SELECT AVG(COST)
FROM PRODUCT_MAST;

Output:

67.00

4. MAX Function

MAX function is used to find the maximum value of a certain column. This function determines the largest value of all selected values of a column.

Syntax

MAX()
or
MAX( [ALL|DISTINCT] expression )

Example:

SELECT MAX(RATE)
FROM PRODUCT_MAST;

30 

5. MIN Function

MIN function is used to find the minimum value of a certain column. This function determines the smallest value of all selected values of a column.

Syntax

MIN()
or
MIN( [ALL|DISTINCT] expression )

Example:

SELECT MIN(RATE)
FROM PRODUCT_MAST;

Output:

10