PostgreSQL - HAVING Clause

The PostgreSQL HAVING clause is used to specify conditions with aggregate functions. Note that the PostgreSQL WHERE clause can not be used to specify conditions with aggregate functions.

Syntax

The syntax for using HAVING clause in PostgreSQL is given below:

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

Please note that the HAVING clause must follow the GROUP BY clause in a query and must also precede the ORDER BY clause if used.

Example:

Consider a database containing tables called Employee and Bonus_Paid with the following records:

Table 1: Employee table

Table 2: Bonus_Paid table

• To fetch a list containing number of employees (from Employee table) in each city and only including cities with more than one employees, the query is given below:

  SELECT COUNT(EmpID) AS Number_of_Employee, City  
  FROM Employee
  GROUP BY City
  HAVING COUNT(EmpID) > 1;
  

  
  

  This will produce the result as shown below:

  Number_of_Employee	City
  2	Amsterdam
  3	London

  
  

  To get above table sorted in descending order based on number of employees, the query will be:

  SELECT COUNT(EmpID), City  
  FROM Employee
  GROUP BY City
  HAVING COUNT(EmpID) > 1
  ORDER BY COUNT(EmpID) DESC;
  

  
  

  This result of the query will be:

  Number_of_Employee	City
  3	London
  2	Amsterdam

• Using HAVING clause with JOINs: To fetch a list containing bonus paid to employees in each city and only including cities with more than one employees, the query is given below:

  SELECT A.City, SUM(B.Bonus) AS BonusAmount
  FROM Employee AS A
  INNER JOIN Bonus_Paid AS B
  ON A.EmpID = B.EmpID
  GROUP BY City
  HAVING COUNT(A.EmpID) > 1;
  

  
  

  This result of the following code will be:

  City	BonusAmount
  Amsterdam	1150
  London	1350