SQL. Is it possible? - sql

Question

Oracle
select * from table1;
column1 | column2 | column3 |
a | 2010 | 1 |
a | 2011 | 2 |
a | 2012 | 3 |
b | 2010 | 4 |
b | 2011 | 5 |
b | 2012 | 6 |
c | 2010 | 7 |
c | 2011 | 8 |
c | 2012 | 9 |
Is it possible to do something like this.
column1 | 2010 | 2011 | 2012 |
a | 1 | 2 | 3 |
b | 4 | 5 | 6 |
c | 7 | 8 | 9 |

Answer 1

Yes
SELECT t.column1,
(SELECT SUM(column3) FROM table1
WHERE column1 = t.column1 AND column2 = 2010) AS "2010",
(SELECT SUM(column3) FROM table1
WHERE column1 = t.column1 AND column2 = 2011) AS "2011",
(SELECT SUM(column3) FROM table1
WHERE column1 = t.column1 AND column2 = 2012) AS "2012"
FROM (
SELECT DISTINCT column1 FROM table1
) t
ORDER BY t.column1
Note, I've added the SUM() aggregate function around colum3 in case you may have duplicate values per column1, column2.
Depending on the database you're using, the following equivalent query might be a bit faster:
SELECT t.column1,
(SELECT SUM(column3) FROM table1
WHERE column1 = t.column1 AND column2 = 2010) AS "2010",
(SELECT SUM(column3) FROM table1
WHERE column1 = t.column1 AND column2 = 2011) AS "2011",
(SELECT SUM(column3) FROM table1
WHERE column1 = t.column1 AND column2 = 2012) AS "2012"
FROM table1 t
GROUP BY t.column1
ORDER BY t.column1
Note that you can achieve the same in a more concise way, using the PIVOT clause (as others have suggested). In Oracle 11g, this would translate to:
SELECT column1, "2010", "2011", "2012"
FROM table1
PIVOT (SUM(column3) FOR column2 IN (2010, 2011, 2012))
In any case, I don't know any database that allows for a dynamic number of columns per table expression, without resorting to tricks involving XML or other means of dynamic SQL. Typically, those tricks aren't much faster than what I suggested here. This means, you'll always have to foresee, how many years you want to support as columns, and adapt your query accordingly

Answer 2

try PIVOT in SQL sever
select column1 , [2010],[2011],[2012]
from your_table
PIVOT (MAX(column3) FOR column2 IN ([2010],[2011],[2012])) P
Edit1:
If your Column2 is dynamic, then try this:
DECLARE #cols AS NVARCHAR(MAX),
#query AS NVARCHAR(MAX)
select #cols = STUFF((SELECT distinct ',' + QUOTENAME(column2)
from your_table
FOR XML PATH(''), TYPE
).value('.', 'NVARCHAR(MAX)')
,1,1,'')
set #query = 'SELECT column1 , ' + #cols + ' from your_table
pivot
(
MAX(column3)
for column2 in (' + #cols + ')
) p '
print(#query)
execute(#query)