Collectives™ on Stack Overflow
Find centralized, trusted content and collaborate around the technologies you use most.
Learn more about Collectives
Teams
Q&A for work
Connect and share knowledge within a single location that is structured and easy to search.
Learn more about Teams
In a test at university there was a question; is it possible to use an aggregate function in the
SQL WHERE
clause.
I always thought this isn't possible and I also can't find any example how it would be possible. But my answer was marked false and now I want to know in which cases it is possible to use an aggregate function in the
WHERE
. Also if it isn't possible it would be nice to get a link to the specification where it is described.
–
HAVING is like WHERE with aggregate functions, or you could use a subquery.
select EmployeeId, sum(amount)
from Sales
group by Employee
having sum(amount) > 20000
select EmployeeId, sum(amount)
from Sales
group by Employee
where EmployeeId in (
select max(EmployeeId) from Employees)
–
–
–
–
You haven't mentioned the DBMS. Assuming you are using MS SQL-Server, I've found a T-SQL Error message that is self-explanatory:
"An aggregate may not appear in the
WHERE clause unless it is in a
subquery contained in a HAVING clause
or a select list, and the column being
aggregated is an outer reference"
http://www.sql-server-performance.com/
And an example that it is possible in a subquery.
Show all customers and smallest order for those who have 5 or more orders (and NULL for others):
SELECT a.lastname
, a.firstname
, ( SELECT MIN( o.amount )
FROM orders o
WHERE a.customerid = o.customerid
AND COUNT( a.customerid ) >= 5
AS smallestOrderAmount
FROM account a
GROUP BY a.customerid
, a.lastname
, a.firstname ;
UPDATE.
The above runs in both SQL-Server and MySQL but it doesn't return the result I expected. The next one is more close. I guess it has to do with that the field customerid, GROUPed BY and used in the query-subquery join is in the first case PRIMARY KEY of the outer table and in the second case it's not.
Show all customer ids and number of orders for those who have 5 or more orders (and NULL for others):
SELECT o.customerid
, ( SELECT COUNT( o.customerid )
FROM account a
WHERE a.customerid = o.customerid
AND COUNT( o.customerid ) >= 5
AS cnt
FROM orders o
GROUP BY o.customerid ;
–
–
You can't use an aggregate directly in a WHERE clause; that's what HAVING clauses are for.
You can use a sub-query which contains an aggregate in the WHERE clause.
–
–
–
–
–
See more below link:
http://www.w3resource.com/sql/aggregate-functions/count-having.php#sthash.90csRM4I.dpuf]
http://www.w3resource.com/sql/aggregate-functions/count-having.php
Another solution is to Move the aggregate fuction to Scalar User Defined Function
Create Your Function:
CREATE FUNCTION getTotalSalesByProduct(@ProductName VARCHAR(500))
RETURNS INT
BEGIN
DECLARE @TotalAmount INT
SET @TotalAmount = (select SUM(SaleAmount) FROM Sales where Product=@ProductName)
RETURN @TotalAmount
Use Function in Where Clause
SELECT ProductName, SUM(SaleAmount) AS TotalSales
FROM Sales
WHERE dbo.getTotalSalesByProduct(ProductName) > 1000
GROUP BY Product
References:
Hope helps someone.
If you are using an aggregate function in a where clause then it means you want to filter data on the basis of that aggregation function. In my case, it's SUM(). I'll jump to the solution.
(select * from(select sum(appqty)summ,oprcod from pckwrk_view group by oprcod)AS asd where summ>500)
The inner query is used to fetch results that need to be filtered.
The aggregate function which has to filter out must be given an ALIAS name because the actual name of the column inside an aggregate function is not accessible or recognized by the outer query.
Finally, the filter can be applied to the aliased name of the column in the inner query
–
Thanks for contributing an answer to Stack Overflow!
- Please be sure to answer the question. Provide details and share your research!
But avoid …
- Asking for help, clarification, or responding to other answers.
- Making statements based on opinion; back them up with references or personal experience.
To learn more, see our tips on writing great answers.
