Having Clause in SQL Server

Having Clause in SQL Server with Examples

In this article, I am going to discuss the Having Clause in SQL Server with different types of examples. Please read our previous article where we discussed the Group By Clause with examples. As part of this article, we are going to discuss the following pointers related to SQL Server Group By Clause.

  1. What is Having Clause and its need?
  2. Understanding the Parameters or Arguments of Having Clause.
  3. Syntax and example of Having Clause.
  4. How to use both WHERE and HAVING Clause?
  5. Having Clause Examples using Sum, Count, Min, Max, and Avg function.
What is Having Clause and its need in SQL Server?

The Having Clause in SQL Server is also used for restricting or you can say filtering the data just like the where clause in SQL Server. So, the Having Clause in SQL Server is an additional filter that is applied to the result set. Logically, the having clause filters the rows from the intermediate result set that is built by using the FROM, WHERE, or GROUP BY clauses in the SELECT statement.

The Having clause is typically used with a GROUP BY clause. That means it is used in combination with a GROUP BY clause to restrict the number of groups to be returned by satisfying the condition which is specified using the having clause.

Syntax of SQL Server Having Clause:
SELECT expression1, expression2, expression_n, 
       aggregate_function (expression)
FROM tables
[WHERE conditions]
GROUP BY expression1, expression2, expression_n
HAVING having_condition;
Parameters or Arguments of Having Clause in SQL Server:
  1. aggregate_function: It can be any of the aggregate function such as SUM, COUNT, MIN, MAX, or AVG.
  2. expression1, expression2, expression_n: The expressions which are not encapsulated within an aggregate function must be included in the GROUP BY clause.
  3. Where Conditions: It is optional. If you want to retrieve selected records based on some conditions then you need to specify the conditions using the Where clause in SQL Server.
  4. HAVING having_condition: The Having Clause Condition us used to add a further condition that can be applied only to the aggregated results to restrict the number of groups to be returned. 
Database tables used in this demo:

We are going to use the following Employee table in this demo.

Having Clause in SQL Server with Examples

Please use the below script to create and populate the Employee table with some dummy data.

-- Create Person table
CREATE TABLE Employee
(
  ID INT PRIMARY KEY IDENTITY(1,1),
  Name VARCHAR(100),
  EmailID VARCHAR(100),
  Gender VARCHAR(100),
  Department VARCHAR(100),
  Salary INT,
  Age INT,
  CITY VARCHAR(100)
)
GO

--Insert some test data into Person table
INSERT INTO Employee VALUES('PRANAYA','PRANAYA@G.COM','Male', 'IT', 25000, 30,'MUMBAI')
INSERT INTO Employee VALUES('TARUN','TARUN@G.COM','Male', 'Payroll', 30000, 27,'ODISHA')
INSERT INTO Employee VALUES('PRIYANKA','PRIYANKA@G.COM','Female', 'IT', 27000, 25,'BANGALORE')
INSERT INTO Employee VALUES('PREETY','PREETY@G.COM','Female', 'HR', 35000, 26,'BANGALORE')
INSERT INTO Employee VALUES('RAMESH','RAMESH@G.COM','Male','IT', 26000, 27,'MUMBAI')
INSERT INTO Employee VALUES('PRAMOD','PRAMOD@G.COM','Male','HR', 29000, 28,'ODISHA')
INSERT INTO Employee VALUES('ANURAG','ANURAG@G.COM','Male', 'Payroll', 27000, 26,'ODISHA')
INSERT INTO Employee VALUES('HINA','HINA@G.COM','Female','HR', 26000, 30,'MUMBAI')
INSERT INTO Employee VALUES('SAMBIT','HINA@G.COM','Male','Payroll', 30000, 25,'ODISHA')
INSERT INTO Employee VALUES('MANOJ','MANOJ@G.COM','Male','HR', 30000, 28,'ODISHA')
INSERT INTO Employee VALUES('SWAPNA','SWAPNA@G.COM','Female', 'Payroll', 28000, 27,'MUMBAI')
INSERT INTO Employee VALUES('LIMA','LIMA@G.COM','Female','HR', 30000, 30,'BANGALORE')
INSERT INTO Employee VALUES('DIPAK','DIPAK@G.COM','Male','Payroll', 32000, 25,'BANGALORE')
GO
Filtering Groups in SQL Server:

The Where clause in SQL Server is used to filter the rows before aggregation, whereas the Having clause in SQL Server is used to filter the groups that mean after aggregations. The following 2 queries produce the same result.

Filtering rows using WHERE clause

SELECT City, SUM(Salary) as TotalSalary
FROM Employee
WHERE City = 'MUMBAI'
GROUP BY City

Filtering groups using HAVING clause, after all, aggregations take place.

SELECT City, SUM(Salary) as TotalSalary
FROM Employee
GROUP BY City
HAVING City = 'MUMBAI'

From the performance point of view, we cannot say or we cannot give a guarantee that one method is more efficient than the other one. The SQL Server optimizer checks or analyzes each statement and then selects an efficient way of executing the query. So, try to eliminate the records as soon as possible which you don’t want in your result set.

It is also possible to combine WHERE and HAVING
SELECT City, SUM(Salary) as TotalSalary
FROM Employee
WHERE Gender = 'Male'
GROUP BY City
HAVING City = 'MUMBAI'
Having Clause Using SUM Function:

The below example uses the SUM function to return the name of the department and the total Salary (in associated with the department). The Having Clause will filter the results so that only departments with total Salary greater than 140000 will be returned.

SELECT Department, SUM(Salary) AS Total_Salary
FROM Employee
GROUP BY Department
HAVING SUM(Salary) > 140000;

Having Clause Using SUM Function

Having Clause Using COUNT Function:

The below example uses the COUNT function to return the city and the number of employees (residing in that city). The Having Clause will filter the results so that only cities with more than 4 employees will be returned.

SELECT City, COUNT(*) AS 'Number of employees'
FROM Employee
GROUP BY City
HAVING COUNT(*) > 4;

Having Clause Using COUNT Function

Having Clause Using MIN Function:

The below example uses the MIN function to return the name of each department and the minimum salary in the department. The Having Clause will return only those departments where the minimum salary is greater than 25000.

SELECT Department, MIN(Salary) AS 'Lowest salary'
FROM Employee
GROUP BY Department
HAVING MIN(Salary) > 25000;

Having Clause Using MIN Function

Having Clause Using MAX Function:

The below example uses the MAX function to return the name of each department and the maximum salary in each department. The Having Clause will return only those departments where the maximum salary is greater than 27000.

SELECT Department, MAX(Salary) AS 'Highest salary'
FROM Employee
GROUP BY Department
HAVING MAX(Salary) > 27000;

Having Clause Using MAX Function

Having Clause Using AVG Function:

The below example uses the AVG function to return the name of each department and the Average salary of each department. Having clause will return only those departments where the average salary is greater than 27000.

SELECT Department, AVG(Salary) AS 'Average salary'
FROM Employee
GROUP BY Department
HAVING AVG(Salary) > 27000;

Having Clause Using AVG Function

In the next article, I am going to discuss the differences between the having and where clauses in SQL Server. Here, in this article, I try to explain Having Clause in SQL Server with some simple examples. 

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