Having (SQL)

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A HAVING clause in SQL specifies that an SQL SELECT statement should only return rows where aggregate values meet the specified conditions. It was added to the SQL language because the WHERE keyword could not be used with aggregate functions.[1]

Examples[edit]

To return a list of department IDs whose total sales exceeded $1000 on the date of January 1, 2000, along with the sum of their sales on that date:

 SELECT DeptID, SUM(SaleAmount)
 FROM Sales
 WHERE SaleDate = '01-Jan-2000'
 GROUP BY DeptID
 HAVING SUM(SaleAmount) > 1000

Referring to the sample tables in the Join example, the following query will return the list of departments which have more than 1 employee:

 SELECT DepartmentName, COUNT(*) 
 FROM Employee, Department 
 WHERE Employee.DepartmentID = Department.DepartmentID 
 GROUP BY DepartmentName
 HAVING COUNT(*)>1;

HAVING is convenient, but not necessary. Code equivalent to the example above, but without using HAVING, might look like:

SELECT * FROM (
   SELECT DepartmentName AS deptNam, COUNT(*) AS empCnt
   FROM Employee AS emp, Department AS dept
   WHERE emp.DepartmentID = dept.DepartmentID
   GROUP BY deptNam
) AS grp
WHERE grp.empCnt > 1;

References[edit]

  1. ^ "SQL HAVING Clause". w3schools.com. "The HAVING clause was added to SQL because the WHERE keyword could not be used with aggregate functions." 

External links[edit]