Can we do partition date wise? - sql

Question

I am new to the concept of Partition. I know horizontal partition but can we do partition date - wise?
in my project I want that whenever we enter in new-year, partition should be created. Can anyone explain how to do this? I am working on ERP sw and it has data of past year and I need partition on year wise.(for example APR-2011 to MAR-2012 is a year)

Answer 1

I think what you are looking for is something like this:
DECLARE #referenceDate datetime = '3/1/2011'
SELECT
[sub].[Period] + 1 AS [PeriodNr],
YEAR(DATEADD(YEAR, [sub].[Period], #referenceDate)) AS [PeriodStartedIn],
COUNT(*) AS [NumberOfRecords],
SUM([sub].[Value]) AS [TotalValue]
FROM
(
SELECT
*,
FLOOR(DATEDIFF(MONTH, #referenceDate, [timestamp]) / 12.0) AS [Period]
FROM [erp]
WHERE [timestamp] >= #referenceDate
) AS [sub]
GROUP BY [sub].[Period]
ORDER BY [sub].[Period] ASC
The fiddle is found here.

Answer 2

When you say partitioning I am curious if you mean in a windowed function or just grouping data in general. Let me show you two ways to aggregate data with partitioning it in a self demonstrating example:
declare #Orders table( id int identity, dt date, counts int)
insert into #Orders values ('1-1-12', 2),('1-1-12', 3),('1-18-12', 1),('2-11-12', 5),('3-1-12', 2),('6-1-12', 8),('10-1-12', 2),('1-13-13', 8)
-- To do days I need to do a group by
select
dt as DayDate
, SUM(counts) as sums
from #Orders
group by dt
-- To do months I need to group differently
select
DATEADD(month, datediff(month, 0, dt), 0) as MonthDate
-- above is a grouping trick basically stating count from 1/1/1900 the number of months of difference from my date field.
--This will always yield the current first day of the month of a date field
, SUM(counts) as sums
from #Orders
group by DATEADD(month, datediff(month, 0, dt), 0)
-- well that is great but what if I want to group different ways all at once?
-- why windowed functions rock:
select
dt
, counts
, SUM(counts) over(partition by DATEADD(year, datediff(year, 0, dt), 0)) as YearPartitioning
, SUM(counts) over(partition by DATEADD(month, datediff(month, 0, dt), 0)) as MonthPartitioning
-- expression above will work for year, month, day, minute, etc. You just need to add it to both the dateadd and datediff functions
, SUM(counts) over(partition by dt) as DayPartitioning
from #Orders
The important concepts on grouping is the traditional group by clause which you MUST LIST that which is NOT performing a math operation on as a pivot to do work on. So in my first select I just chose date and then said sum(counts). It then saw on 1-1-12 it had two values so it added both of them and on everything else it added them individually. On the second select method I perform a trick on the date field to make it transform to the first day of the month. Now this is great but I may want all of this at once.
Windowed functions do groupings inline, meaning they don't need a grouping clause as that is what the over() portion is doing. It however may repeat the values since you are not limiting your dataset. This means that if you look at the third column of the third select 'YearPartitioning' it repeats the number 23 seven times. WHy? Well because you never told the statement to do any grouping outside the function so it is showing every row. The number 23 will occur as long as the expression is true that the year is the same for all values. Just remember this when selecting from a windowed expression.