Get ROWS as COLUMNS (SQL Server dynamic PIVOT query) - sql-server

Question

I'm using MS SQL 2008 R2, have three tables with following schema:
Table 1: Contains workshift info for each worker
CREATE TABLE workshift (
[ws_id] [bigint] NOT NULL,
[start_date] [datetime] NOT NULL,
[end_date] [datetime] NOT NULL,
[worker_id] [bigint] NOT NULL
)
INSERT INTO workshift VALUES (1, '2012-08-20 08:30:00', '2012-08-20 14:30:00', 1)
INSERT INTO workshift VALUES (2, '2012-08-20 14:30:00', '2012-08-20 22:30:00', 2)
Table 2: Contains monetary denominations
CREATE TABLE currency_denom (
[cd_id] [decimal](7, 2) NOT NULL,
[name] [nchar](100) NOT NULL
)
INSERT INTO currency_denom VALUES (1, '100.00')
INSERT INTO currency_denom VALUES (2, '50.00')
INSERT INTO currency_denom VALUES (3, '20.00')
INSERT INTO currency_denom VALUES (4, '10.00')
INSERT INTO currency_denom VALUES (5, '5.00')
INSERT INTO currency_denom VALUES (6, '1.00')
Table 3: Contains the quantity of each denomination the worker has received in every workshift
CREATE TABLE currency_by_workshift (
[cd_id] [decimal](7, 2) NOT NULL,
[ws_id] [bigint] NOT NULL,
[qty] [int] NOT NULL
)
INSERT INTO currency_by_workshift VALUES (1, 1, 1)
INSERT INTO currency_by_workshift VALUES (2, 1, 2)
INSERT INTO currency_by_workshift VALUES (3, 1, 2)
INSERT INTO currency_by_workshift VALUES (2, 2, 3)
INSERT INTO currency_by_workshift VALUES (4, 2, 4)
INSERT INTO currency_by_workshift VALUES (5, 2, 2)
I need to get the currency_by_workshift values in columns instead of rows, along with the workshift values, that is:
workshift | workshift | workshift | 100.00 | 50.00 | 20.00 | 10.00 | 5.00 | 1.00
ws_id | start_date | end_date | | | | | |
1 | 2012-08-20 08:30:00 | 2012-08-20 14:30:00 | 1 | 2 | 2 | 0 | 0 | 0
2 | 2012-08-20 14:30:00 | 2012-08-20 22:30:00 | 0 | 2 | 0 | 4 | 2 | 0
I'm not able to use a case to count quantities for each currency denomination because they are configurable, if a new denomination is added, the query should be modified. Same applies if using PIVOT function, or I'm wrong?
How can I get the info that way?

Answer 1

What you are trying to do is called a PIVOT. There are two ways to do this, either with a Static Pivot or a Dynamic Pivot.
Static Pivot - is where you will hard-code the values of the rows to transform to columns (See SQL Fiddle with Demo):
select ws_id,
start_date,
end_date,
IsNull([100.00], 0) [100.00],
IsNull([50.00], 0) [50.00],
IsNull([20.00], 0) [20.00],
IsNull([10.00], 0) [10.00],
IsNull([5.00], 0) [5.00],
IsNull([1.00], 0) [1.00]
from
(
select ws.ws_id,
ws.start_date,
ws.end_date,
cd.name,
cbw.qty
from workshift ws
left join currency_by_workshift cbw
on ws.ws_id = cbw.ws_id
left join currency_denom cd
on cbw.cd_id = cd.cd_id
) x
pivot
(
sum(qty)
for name in ([100.00], [50.00], [20.00], [10.00], [5.00], [1.00])
) p
Dynamic pivot is where the columns are determined at run-time (see SQL Fiddle with Demo):
DECLARE #cols AS NVARCHAR(MAX),
#query AS NVARCHAR(MAX),
#colsPivot AS NVARCHAR(MAX)
select #colsPivot =
STUFF((SELECT ', IsNull(' + QUOTENAME(rtrim(name)) +', 0) as ['+ rtrim(name)+']'
from currency_denom
GROUP BY name
ORDER BY cast(name as decimal(10, 2)) desc
FOR XML PATH(''), TYPE
).value('.', 'NVARCHAR(MAX)')
,1,1,'')
select #cols = STUFF((SELECT distinct ', ' + QUOTENAME(name)
from currency_denom
FOR XML PATH(''), TYPE
).value('.', 'NVARCHAR(MAX)')
,1,1,'')
set #query
= 'SELECT ws_id, start_date, end_date,' + #colsPivot + ' from
(
select ws.ws_id,
ws.start_date,
ws.end_date,
cd.name,
cbw.qty
from workshift ws
left join currency_by_workshift cbw
on ws.ws_id = cbw.ws_id
left join currency_denom cd
on cbw.cd_id = cd.cd_id
) x
pivot
(
sum(qty)
for name in (' + #cols + ')
) p '
execute(#query)
Both versions will produce the same results.

Answer 2

#bluefeet provided a very good answer utilizing the built in PIVOT functionality. However, I frequently find the PIVOT and UNPIVOT nomenclature confusing and I have yet to encounter a situation where the same results can't be achieved with standard aggregations:
select w.ws_id, w.start_date, w.end_date,
[100.00] = isnull(sum(case when c.name='100.00' then cw.qty else null end), 0),
[50.00] = isnull(sum(case when c.name='50.00' then cw.qty else null end), 0),
[20.00] = isnull(sum(case when c.name='20.00' then cw.qty else null end), 0),
[10.00] = isnull(sum(case when c.name='10.00' then cw.qty else null end), 0),
[5.00] = isnull(sum(case when c.name='5.00' then cw.qty else null end), 0),
[1.00] = isnull(sum(case when c.name='1.00' then cw.qty else null end), 0)
from workshift w
join currency_by_workshift cw on w.ws_id=cw.ws_id
join currency_denom c on cw.cd_id=c.cd_id
group by w.ws_id, w.start_date, w.end_date
If you want to do a dynamic pivot, you only need to build a string of the pivot columns once:
DECLARE #cols AS NVARCHAR(MAX),
#query AS NVARCHAR(MAX)
select #cols =
stuff(( select replace(',[#name] = isnull(sum(case when c.name=''#name'' then cw.qty else null end), 0)'
, '#name', rtrim(name))
from currency_denom
order by cd_id
for xml path(''), type
).value('.', 'nvarchar(max)')
,1,1,'')
select #query = '
select w.ws_id, w.start_date, w.end_date, '+#cols+'
from workshift w
join currency_by_workshift cw on w.ws_id=cw.ws_id
join currency_denom c on cw.cd_id=c.cd_id
group by w.ws_id, w.start_date, w.end_date
'
execute(#query)