Need SQL statement to create a list of unique month numbers (ie: integer 1 - 12) of dates found in a daterange

pbissegger
pbissegger used Ask the Experts™
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I need to create a list of unique month numbers (ie: 1- 12) from a datetime field for dates in a date range, and would like to order the month numbers by date ascending

So if I had the following dates:
  - November 23, 2012
  - December 2, 2012
  - December 14, 2012
  - November 12, 2012
  - December 22, 2012
  - February 4, 2013

then I would like the output to be:
  - 11
  - 12
  - 2

The dates are all in a datetime format

I have tried both the Distinct and Group by clauses but I am struggling to find something that works.

(ie: something like 'Select distinct(month(gamedatetime)) from games order by gamedatetime asc' which now throws me an error)  

Thanks, Peter
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John EastonDirector

Commented:
I would have suggested going with a formula similar to what you have suggested.

Firstly, is the field a Datetime type?

Irnocially, testing this in MS SQL your formula works.  Which DBMS are you using?
Éric MoreauSenior .Net Consultant
Top Expert 2016

Commented:
which error?

Author

Commented:
The error is:

ORDER BY items must appear in the select list if SELECT DISTINCT is specified.

I am using an MSSQL database (probably 2005).

But I cannot change it to 'ORDER BY month(gamedatetime)' (which does not throw an error) because that gives me a numerical order from 1 - 12.... and not a series of months in order of date.

For example, if I have a hockey season the months will span from September to April (which is 9 - 4...)

Peter
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John EastonDirector

Commented:
The problem is you are trying to sort by the date, when the date is not in the query.

Try:  Select distinct(month(gamedatetime)) AS Months From games Order By Months asc
Most Valuable Expert 2012
Top Expert 2014
Commented:
Try following

Select distinct(month(gamedatetime)) from (Select gamedatetime From games order by gamedatetime asc)

Author

Commented:
Here's the results:

1. I did not think that the JEaston solution would work, and it did not. It returned a list in numerical order (ie: 1,2,3,4) even though the months do not appear in this order (ie: they are 9,10,11, 1,2,3) when I just list out the dates in ascending order from the database.

2. I thought that CodeCruiser's solution would work, but it did not. Logically, the code is correct. When I run the inner SQL statement I get a list of all the dates in the right order, but when I run the 'Select Distinct(month(gamedatetime)) from' in front of it, it reorders it into Numerical order.

Why ? It doesn't make any sense

I then tried different versions of Codecruiser's suggestion, including:

a) replacing the Distinct by a Group By
b) Putting the Months(gamedatetime) inside the inner SQL, and just having a 'Select Distinct from ' clause outside on its own
c) Same as (b) but with the Group By Clause

All of them have the inner SQL working perfectly, but using the Distinct or Group By Clauses reorders it.

Any suggestions ?
Director
Commented:
Sorry, I missed that the output should still be month/year order.

What about something like:  Select distinct month(gamedatetime) AS Months, year(gamedatetime) AS Years From games Order By Years asc, Months asc

Downside, it outputs the 'Years' column which you do not want, but it orders correctly.  I'm sure there is a neater way - but as it's midnight here my brain is not comming up with anything better!

Author

Commented:
Excellent solution by JEaston.

I think also CodeCruiser's solution was solid, but possibly there is a bug in MSSQL 2005.

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