Summary Stats and Corresponding Dates - SQL Server - sql

Question

I was hoping someone perhaps could help. This problem was presented to me recently and I thought it would be easy, but (personally) found it a bit of a struggle. I can do it in Excel and SSRS - but I was curious if I was able to do it in SQL Server...
I would like to create a set of summary statistics (Max, Min) for a dataset. Easy enough... But I wanted to associate the corresponding date with those values.
Here is what my data looks like:
I have yearly data (not exactly - but beside the point) and I produce a pivoted summary like this using a series of CASE WHEN statements. This is fine - the output is seen on the right (above).
Each time I output this data - I like to provide a summary of the all the historic data (I only show the most recent data for sake of brevity). So... The question is how do I take an output like the one shown below (on different dates) and provide a summary data set like the one I have on the right?
So - a little background. I have already managed to join the Min and Max values using a UNION and that bit is fine. The tricky bit (I think) is how to form an INNER JOIN, using a sub query, with the Max or Min result values to return the corresponding Max or Min date, for each Type? Now it is highly likely that I am being a bit of an idiot and missing something obvious....but... Would really appreciate any help from anyone...
Many thanks in advance

Answer 1

This query will do the job, and for all TYPE
SELECT
Description, [CAR], [CAT], [MAT], [EAT], [PAR], [MAR], [FAR], [MOT], [LOT], [COT], [ROT]
FROM
(SELECT
unpvt.TYPE
,unpvt.Description
,unpvt.value
FROM (
SELECT
t.TYPE
,CONVERT(sql_variant,MAX(maxResult.MAX_RESULT)) as MAX_RESULT
,CONVERT(sql_variant,MIN(minResult.MIN_RESULT)) as MIN_RESULT
,CONVERT(sql_variant,MAX(CASE WHEN maxResult.MAX_RESULT IS NOT NULL THEN t.DATE ELSE NULL END)) as MAX_DATE
,CONVERT(sql_variant,MIN(CASE WHEN minResult.MIN_RESULT IS NOT NULL THEN t.DATE ELSE NULL END)) as MIN_DATE
FROM
table_name t -- You need to set your table name
LEFT JOIN (SELECT
TYPE
,MIN(RESULT) as MIN_RESULT
FROM
table_name -- You need to set your table name
GROUP BY
TYPE) minResult
on minResult.TYPE = t.TYPE
and minResult.MIN_RESULT = t.RESULT
LEFT JOIN (SELECT
TYPE
,MAX(RESULT) as MAX_RESULT
FROM
table_name -- You need to set your table name
GROUP BY
TYPE) maxResult
on maxResult.TYPE = t.TYPE
and maxResult.MAX_RESULT = t.RESULT
GROUP BY
t.TYPE) U
unpivot (
value
for Description in (MAX_RESULT, MIN_RESULT, MAX_DATE, MIN_DATE)
) unpvt) P
PIVOT
(
MAX(value)
FOR TYPE IN ([CAR], [CAT], [MAT], [EAT], [PAR], [MAR], [FAR], [MOT], [LOT], [COT], [ROT])
)AS PVT
DEMO : SQLFIDDLE
CONVERT(sql_variant, is a cast for columns to a common data type. This is a requirement of the UNPIVOT operator when you are running with subquery FROM.

Answer 2

It is possible to use the PIVOT command if your SQLServer is 2005 or better, but the raw data for the pivot need to be in a specific format, and the query I came up with is ugly
WITH minmax AS (
SELECT TYPE, RESULT, [date]
, row_number() OVER (partition BY TYPE ORDER BY TYPE, RESULT) a
, row_number() OVER (partition BY TYPE ORDER BY TYPE, RESULT DESC) d
FROM t)
SELECT info
, cam = CASE charindex('date', info)
WHEN 0 THEN cast(cast(cam AS int) AS varchar(50))
ELSE cast(cam AS varchar(50))
END
, car = CASE charindex('date', info)
WHEN 0 THEN cast(cast(car AS int) AS varchar(50))
ELSE cast(cam AS varchar(50))
END
, cat = CASE charindex('date', info)
WHEN 0 THEN cast(cast(cat AS int) AS varchar(50))
ELSE cast(cam AS varchar(50))
END
FROM (SELECT TYPE, 'maxres' info, RESULT value FROM minmax WHERE 1 = d
UNION ALL
SELECT TYPE, 'minres' info, RESULT value FROM minmax WHERE 1 = a
UNION ALL
SELECT TYPE, 'maxdate' info , [date] value FROM minmax WHERE 1 = d
UNION ALL
SELECT TYPE, 'mindate' info , [date] value FROM minmax WHERE 1 = a) DATA
PIVOT
(max(value) FOR TYPE IN ([CAM], [CAR], [CAT])) pvt
It's only a proof of concept so in SQLFiddle I have used a reducet set of fake data (3 row per 3 Type)
After the data preparation
SELECT TYPE, 'maxres' info, RESULT value FROM minmax WHERE 1 = d
UNION ALL
SELECT TYPE, 'minres' info, RESULT value FROM minmax WHERE 1 = a
UNION ALL
SELECT TYPE, 'maxdate' info , [date] value FROM minmax WHERE 1 = d
UNION ALL
SELECT TYPE, 'mindate' info , [date] value FROM minmax WHERE 1 = a
the value column is implicitly casted to the more complex datatype, in this case DateTime (you cannot have different data type in the same column), to see the data in the intended way an explicit cast is in needed, and is done with the CASE and CAST in
, cam = CASE charindex('date', info)
WHEN 0 THEN cast(cast(cam AS int) AS varchar(50))
ELSE cast(cam AS varchar(50))
END
the CASE check the data type, looking for the substring 'date' in the info column, then cast the row value back to INT for the minres and maxres column and in any case cast the value to varchar(50) to have the same data type again
UPDATE
With the sql_variant the CASE CAST block is not needed, thanks Ryx5
WITH minmax AS (
SELECT TYPE, RESULT, [date]
, row_number() OVER (partition BY TYPE ORDER BY TYPE, RESULT) a
, row_number() OVER (partition BY TYPE ORDER BY TYPE, RESULT DESC) d
FROM table_name)
SELECT info
, [CAM], [CAR], [CAT]
FROM (SELECT TYPE, 'maxres' info, cast(RESULT as sql_variant) value
FROM minmax WHERE 1 = d
UNION ALL
SELECT TYPE, 'minres' info, cast(RESULT as sql_variant) value
FROM minmax WHERE 1 = a
UNION ALL
SELECT TYPE, 'maxdate' info , cast([date] as sql_variant) value
FROM minmax WHERE 1 = d
UNION ALL
SELECT TYPE, 'mindate' info , cast([date] as sql_variant) value
FROM minmax WHERE 1 = a) DATA
PIVOT
(max(value) FOR TYPE IN ([CAM], [CAR], [CAT])) pvt