How to Use Group By clause when we use Aggregate function in the Joins?
Solution 1
GROUP BY
for any unique combination of the specified columns does aggregation (like sum, min etc). If you don't specify some column name in the GROUP BY
clause or in the aggregate function its unknown to the SQL engine which value it should return for that kind of column.
Solution 2
GROUP BY (Transact-SQL) groups a selected set of rows into a set of summary rows by the values of one or more columns or expressions in SQL Server 2008 R2. One row is returned for each group. Aggregate functions in the SELECT clause list provide information about each group instead of individual rows.
SELECT a.City, COUNT(bea.AddressID) AS EmployeeCount
FROM Person.BusinessEntityAddress AS bea
INNER JOIN Person.Address AS a
ON bea.AddressID = a.AddressID
GROUP BY a.City
The GROUP BY clause has an ISO-compliant syntax and a non-ISO-compliant syntax. Only one syntax style can be used in a single SELECT statement. Use the ISO compliant syntax for all new work. The non-ISO compliant syntax is provided for backward compatibility.
In ISO-compliant syntax each table or view column in any nonaggregate expression in the list must be included in the GROUP BY
list.
select pub_id, type, avg(price), sum(total_sales)
from titles
group by pub_id, type
Refering to Organizing query results into groups: the group by clause
Sybase or non-ISO-compliant syntax lifts restrictions on what you can include or omit in the
select
list of a query that includesgroup by
:
The columns in the select list are not limited to the grouping columns and columns used with the vector aggregates.
The columns specified by group by are not limited to those non-aggregate columns in the select list.
Example:
select type, title_id, avg(price), avg(advance)
from titles
group by type
Solution 3
To use aggregate functions like sum without group by, use the over clause.
See: http://msdn.microsoft.com/en-us/library/ms189461.aspx
Example:
CREATE TABLE #a (ida int, name varchar(50))
CREATE TABLE #b (ida int, number int)
INSERT INTO #a VALUES(1,'one')
INSERT INTO #a VALUES(2,'two')
INSERT INTO #b VALUES(1,2)
INSERT INTO #b VALUES(1,3)
INSERT INTO #b VALUES(2,1)
SELECT DISTINCT a.ida, sum(number) OVER (PARTITION BY a.ida) FROM #a a
INNER JOIN #b b on a.ida = b.ida
thevan
Software Engineering Senior Analyst at Accenture Solutions Private Limited, Chennai, India. Interested in ASP.Net, MVC, Web API, WCF, Web Services, ADO.Net, C#.Net, VB.Net, Entity Framework, MS SQLServer, Angular.js, JavaScript, JQuery, Ajax, HTML and CSS
Updated on December 10, 2020Comments
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thevan over 3 years
I want to join three tables and to calculate the Sum(Quantity) of the Table A. I tried something and I get the desired output. But still I have confusion based on aggregate function and Group By clause.
While calculating the sum value by joining two or more tables, what are the columns we need to mention in the Group By clause and why do we need to give those columns?
For Example: Here is my table and the desired query.
TableA: ItemID, JobOrderID, CustomerID, DivisionID, Quantity TableB: ItemID, ItemName, SpecificationID TableC: SpecificationID, SpecificationName TableD: DivisionID, DivisionName TableE: JobOrderID, JobOrderNo. TableF: CustomerID, CustomerName
I want to get the Sum(Quantity) based on
ItemID
,CustomerID
,JobOrderID
andDivisionID
.I wrote the following query and it's working fine. But if I remove any column in the Group By clause, it doesn't give the desired result. Why? What does the Group By clause do here? How to specify the Group By clause when using Aggregate function? Here is my Query.
SELECT B.ItemName + ' - ' + C.SpecificationName AS 'ItemName', SUM(A.Quantity) AS 'Quantity', A.ItemID, D.DivisionName, F.CustomerName, E.JobOrderNo, A.DivisionID, A.JobOrderID, A.CustomerID FROM TableA A INNER JOIN TableB B ON B.ItemID = A.ItemID INNER JOIN TableC C ON C.SpecificationID = B.SpecificationID INNER JOIN TableD D ON D.DivisionID = A.DivisionID LEFT JOIN TableE E ON E.JobOrderID = A.JobOrderID LEFT JOIN TableF F ON F.CustomerID = A.CustomerID WHERE A.ItemID = @ItemID GROUP BY A.ItemID, A.JobOrderID, A.DivisionID, A.CustomerID, D.DivisionName, F.CustomerName, E.JobOrderNo, B.ItemName, C.SpecificationName
Any one please give suggestion about the Group By Clause by considering this as an example.
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thevan almost 13 yearsSo if we select some columns means, we need to give those columns in the Group By clause too. Is it so?
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thevan almost 13 yearsSo if we select some columns means, we need to give those columns in the Group By clause too. Is it so?
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Piotr Auguscik almost 13 yearsYes, selected column must be in
group by
or in agreagtion like:select max(column_name)
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william.eyidi over 6 yearsthis makes a lot more sense, group by only show a reprensentative row for the group therefore all the non aggregate fields should be included into the group by clause.