MSSQL Order by date with distinct - sql

Question

I have this query segment below where I'm trying to build a string of "month-year" from a date field in this table. It's very important that it comes in the right order starting from current month going forward 12 months.
DECLARE #cols AS NVARCHAR(MAX)
SELECT #cols = STUFF(
(SELECT N',' + QUOTENAME(y) AS [text()]
FROM (SELECT DISTINCT CONVERT(char(3), StartDate, 0) + '-' +
RIGHT(CONVERT(varchar, YEAR(StartDate)), 2) AS y
FROM Products2
) AS Y
--ORDER BY y desc
FOR XML PATH('')),
1, 1, N'')
This query isn't pulling the dates in the right order and I wanted to see if you guys know of any neat tricks to pull the dates in the correct order. I can bring in the startDate column and sort it by that but it brings in duplicates as it may have several entries for the same month. I've created a sample table here http://sqlfiddle.com/#!6/3a500/5

Answer 1

You could use
DECLARE #cols AS NVARCHAR(MAX);
SELECT #cols = STUFF((SELECT N',' + QUOTENAME(y) AS [text()]
FROM (SELECT CONVERT(CHAR(3), StartDate, 0) + '-'
+ RIGHT(CONVERT(VARCHAR, YEAR(StartDate)), 2) AS y,
MIN(StartDate) AS z
FROM Products2
GROUP BY CONVERT(CHAR(3), StartDate, 0) + '-'
+ RIGHT(CONVERT(VARCHAR, YEAR(StartDate)), 2)) AS Y
ORDER BY z
FOR XML PATH('')), 1, 1, N'');
SELECT #cols;
SQL Fiddle

Answer 2

It looks like you just getting the month/year so we can truncate to the first day of the month and include that in the query.
DATEADD(month, DATEDIFF(month, 0, StartDate), 0) monthStart
Now we can order by it:
DECLARE #cols AS NVARCHAR(MAX);
SELECT #cols = STUFF(
(SELECT N',' + QUOTENAME(y) AS [text()]
FROM (
SELECT DISTINCT CONVERT(char(3), StartDate, 0) + '-' +
RIGHT(CONVERT(varchar, YEAR(StartDate)), 2) AS y,
DATEADD(month, DATEDIFF(month, 0, StartDate), 0) monthStart
FROM Products2
) AS Y
ORDER BY monthStart
FOR XML PATH('')),
1, 1, N'');
select #cols;
This is the output:
[Dec-15],[Jan-16],[Feb-16],[Mar-16],[Apr-16],[May-16],[Jun-16],[Jul-16],[Aug-16],[Sep-16],[Oct-16],[Nov-16],[Dec-16]
Is that what you are looking for? Here is a fiddle:
http://sqlfiddle.com/#!6/3a500/67
Better yet, just select the distinct month start dates and then only do the string conversion on that.
DECLARE #cols AS NVARCHAR(MAX);
SELECT #cols = STUFF(
(SELECT N',' + QUOTENAME(CONVERT(char(3), monthStart, 0) + '-' +
RIGHT(CONVERT(varchar, YEAR(monthStart)), 2)) AS [text()]
FROM (
SELECT DISTINCT
DATEADD(month, DATEDIFF(month, 0, StartDate), 0) monthStart
FROM Products2
) AS Y
ORDER BY monthStart
FOR XML PATH('')),
1, 1, N'');
select #cols;
Here is that fiddle:
http://sqlfiddle.com/#!6/3a500/72

Answer 3

If you are using SQL Server 2012+ you could use FORMAT function:
DECLARE #cols AS NVARCHAR(MAX);
;WITH cte AS -- get only one date per month/year
(
SELECT MIN(StartDate) AS StartDate
FROM #Products2
GROUP BY YEAR(StartDate),MONTH(StartDate)
)
SELECT #cols = STUFF((SELECT ',' + QUOTENAME(FORMAT(StartDate, 'MMM-yy'))
FROM cte
ORDER BY StartDate
FOR XML PATH('')),
1, 1, N'');
SELECT #cols;
LiveDemo
Output:
╔══════════════════════════════════════════════════════════════════════════════════════════════════════════════════════╗
║ result ║
╠══════════════════════════════════════════════════════════════════════════════════════════════════════════════════════╣
║ [Dec-15],[Jan-16],[Feb-16],[Mar-16],[Apr-16],[May-16],[Jun-16],[Jul-16],[Aug-16],[Sep-16],[Oct-16],[Nov-16],[Dec-16] ║
╚══════════════════════════════════════════════════════════════════════════════════════════════════════════════════════╝