How to calculate average of a column and then include it in a select query in oracle?

How to calculate average of a column and then include it in a select query in oracle?

My table is--

create table mobile  (    id integer,    m_name  varchar(20),    cost integer  )  

and the values are --

insert into mobile values(10,'NOkia',100);  insert into mobile values(11,'Samsung',150);  insert into mobile values(12,'Sony',120);  

I know how to calculate average on column cost, my code is--

 select avg(cost) from mobile;  

and the result is 123

But i want to calculate average and then also show the difference.I was able to this but, I am not able to add avg column in the select query--

My code is ---

SELECT id, m_name as "Mobile Name", cost as Price,avg(cost) as Average,  cost-(select avg(cost) from mobile) as Difference FROM mobile  group by id,m_name,cost;  

and the output is --

id      Mobile Name   Price  Average  Difference   10      Nokia         100    100      -23  11      Samsung       150    150       27  12      Sony          120    120      -3  

what I wants is to correct this average column.. I wants this---

id      Mobile Name  Price  Average  Difference   10      Nokia       100     123     -23  11      Samsung     150     123      27  12      Sony        120     123      -3  

please help...

Answer by Angelo Fuchs for How to calculate average of a column and then include it in a select query in oracle?

try

SELECT id, m_name as "Mobile Name", cost as Price,(select avg(cost) from mobile) as Average),  cost-(select avg(cost) from mobile) as Difference FROM mobile  group by id,m_name,cost;  

if your query is too expensive that way drop me a commend then I'll improve it.

Answer by ruakh for How to calculate average of a column and then include it in a select query in oracle?

The simplest change is to change avg(cost) as Average to (select avg(cost) from mobile) as Average. This also means that you won't need the GROUP BY clause anymore (since it doesn't do what you actually wanted):

SELECT id,         m_name AS "Mobile Name",         cost AS "Price",         (SELECT AVG(cost) FROM mobile) AS "Average",         cost - (SELECT AVG(cost) FROM mobile) AS "Difference"    FROM mobile  ;  

Answer by Justin Pihony for How to calculate average of a column and then include it in a select query in oracle?

Your group by is what aggregates your average, and it is grouping by the whole table (I am assuming you did this to allow the select for everything) Just move your avg into another subquery, remove the overarching group by and that should solve it.

SELECT id, m_name AS "Mobile Name", cost AS Price,      (SELECT

AVG(cost) FROM mobile) AS Average, cost-(SELECT AVG(cost) FROM mobile) AS Difference FROM mobile;

When you run the basic SELECT AVG(cost) statement it is naturally grouping by the column specified (cost in this case) as that is what you are requesting. I would suggest reading up more on GROUP BY and aggregates to get a better grasp on the concept. That should help you more than just a simple solution.

UPDATE:

The answer below is actually from David's answer. It makes use the analytical functions. Basically, what is happening is that on each AVG call, you are telling the engine what to use for the function (in this case, nothing). A decent writeup on analytical functions can be found here and here and more with a google on the matter.

SELECT id, m_name AS "Mobile Name" cost AS Price, AVG(cost) OVER( ) AS Average,       cost - AVG(cost) OVER ( ) AS Difference      FROM mobile  

However, if your SQL engine allows for variables, you could just as easily do the below answer. I actually prefer this for future maintainability/readability. The reason is that a variable with a good name can be very descriptive to future readers of the code, versus an analytical function that does require a little bit more work to read (especially if you do not understand the over function).

Also, this solution duplicates the same query twice, so it might be worth storing your average in a SQL variable. Then you ca change your statement to simply use that global average

This is variables in SQL-Server (you will have to adapt it for your own instance of SQL)

DECLARE @my_avg INT;  SELECT @my_avg = AVG(cost) FROM Mobile;        SELECT id, m_name AS "Mobile Name", cost AS Price,          @my_avg AS Average, cost-@my_avg AS Difference       FROM mobile;  

This solution will read a lot cleaner to future readers of your SQL, too

Answer by tawman for How to calculate average of a column and then include it in a select query in oracle?

One of the rare times a CROSS JOIN is applicable:

WITH avgcost as (select round(avg(cost)) as Average from mobile)  SELECT id, m_name as "Mobile Name", cost as Price, Average,  cost-Average as Difference  FROM mobile cross join avgcost  

Which will result in:

ID  Mobile Name PRICE   AVERAGE DIFFERENCE  10  NOkia       100     123     -23  11  Samsung     150     123     27  12  Sony        120     123     -3  

Answer by David Faber for How to calculate average of a column and then include it in a select query in oracle?

Since you're using Oracle, you should be able to use AVG() as an analytic (window) function:

SELECT id, m_name AS "Mobile Name" cost AS Price, AVG(cost) OVER( ) AS Average       , cost - AVG(cost) OVER ( ) AS Difference    FROM mobile  

No need for subqueries or GROUP BY.

Answer by RAJU for How to calculate average of a column and then include it in a select query in oracle?

select pid, name, price as actualcost,          AVERAGE = (select AVG(price) from Part_Master),          price - (select AVG(price) as diff from Part_Master) AS COST_DIFF   from   Part_Master  

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