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HAVING Clause

Unlike where clause which imposes conditions on columns Having clause enables you to specify conditions that filter which group results appear in the results.

Syntax

SELECT column_name(s)
FROM table_name
WHERE condition
GROUP BY column_name(s)
HAVING condition
ORDER BY column_name(s);

Description

• Used with aggregate functions
• Must follow GROUP BY clause in the query

Aggregate Functions

• SQL aggregation is the task of collecting a set of values to return a single value.
• An aggregate function is a function where the values of multiple rows are grouped together as input on certain criteria to form a single value of more significant meaning.

Aggregate Functions Examples

Suppose this are the table given to us

Students	table
rollno	name	class
1	Sanskriti	TE
1	Shree	BE
2	Harry	TE
3	John	TE
3	Shivani	TE

purchase	table
item	price	customer_name
Pen	10	Sanskriti
Bag	1000	Sanskriti
Vegetables	500	Sanskriti
Shoes	5000	Sanskriti
Water Bottle	800	XYZ
Mouse	120	ABC
Sun Glasses	1350	ABC

AVG function

Calculates average of the given column of values

SELECT AVG(price) AS Avg_Purchase, customer_name
FROM purchase
GROUP BY customer_name;

Avg_Purchase	customer_name
1627.5000	Sanskriti

SUM function

Calculates sum of values of given column.

SELECT SUM(price) AS Total_Bill, customer_name
FROM purchase
GROUP BY customer_name;

Total_Bill	customer_name
6510	Sanskriti

COUNT function

Gives count of entries/ values in given column.

SELECT COUNT(item) AS Total_Items, customer_name
FROM purchase
GROUP BY customer_name;

Total_Items	customer_name
4	Sanskriti

MAX function

Return maximum value from the number of values in the column.

SELECT MAX(price) AS Highest_Purchase, customer_name
FROM purchase
GROUP BY customer_name;

Highest_Purchase	customer_name
5000	Sanskriti

MIN function

Return minimum value from the number of values in the column.

SELECT MIN(price) AS Lowest_Purchase, customer_name
FROM purchase
GROUP BY customer_name;

Lowest_Purchase	customer_name
10	Sanskriti

Having clause Examples

Example 1

SELECT COUNT(class) AS strength, class
FROM Students
GROUP BY class
HAVING COUNT(class) > 2;

Above query gives number of students in a class having number of students > 2

strength	class
4	TE

Example 2

SELECT customer_name, MIN(price) AS MIN_PURCHASE
FROM purchase
GROUP BY customer_name
HAVING MIN(price) > 10;

Above query finds minimum price which is > 10

customer_name	MIN_PURCHASE
XYZ	800
ABC	120

Example 3

SELECT customer_name, AVG(price) AS Average_Purchase
FROM purchase
GROUP BY customer_name
HAVING AVG(price) > 550
ORDER BY customer_name DESC;

Above query calculates average of price and prints customer name and average price which is greater than 550 with descending order of customer names.

customer_name	Average_Purchase
XYZ	800.0000
Sanskriti	1627.5000
ABC	735.0000

Example 4

SELECT customer_name, SUM(price) AS Total_Purchase
FROM purchase
WHERE customer_name
LIKE "S%"
GROUP BY customer_name
HAVING SUM(price) > 1000;

Calculates SUM of price and returns customer name and sum > 1000.

customer_name	Total_Purchase
Sanskriti	6510