带JOIN和按平均分组的SQL

Question

I am looking to generate results of my shop efficiencies. To do this I will need data from 3 different tables JOMAST, JODRTG and INRTGS. So I have come up with the following Query:

select jomast.fpartno AS 'Part Number',
JODRTG.foperno AS 'OP Number',
JODRTG.fopermemo As ' Description',
JODRTG.fpro_id AS 'Work Center',
jodrtg.fprod_tim AS ' Act. Production Time',
inrtgs.fuprodtime AS 'Est. Prodution Time'
from jodrtg
Left join jomast on jodrtg.fjobno = jomast.fjobno
left join inrtgs on jomast.fpartno = inrtgs.fpartno

Now what I need to do is average out the Act. Production Time. And get things down to the Part Number with all of the OP numbers for that part.

When I try and Group By JOMAST.fpartno I get an error that it cannot use and outer column. If I do Group By on the Operation number, then all Operation 10's for every part will be combined. Which, is not the desired result.

Can someone please point me in the direction I need to go to achieve my result?

Answer 1

It sounds like you want to have multiple rows all showing the same jodrtg.fpartno , all showing different jodrtg.fprod_tim , but all showing the average (same) value of jodrtg.fprod_tim yes?

If so, add:

AVG(jodrtg.fprod_tim) OVER(PARTITION BY jodrtg.fpartno) as avg_for_all_fprod_tim

as a column in your list of columns you're selecting.

For more info you can google PARTITION BY, but think of it like an instruction to perform a GROUP BY x, AVG(y) (or sum, max, whatever) on the data, but then put that AVG into the row data for each row where x is present..

Essentially it's the same as writing a smaller subquery of (SELECT jodrtg.fpartno, avg(jodrtg.fprod_tim) as avg_for_all_frod_tim FROM blah GROUP BY jodrtg.fpartno) and then joining it back to your main query