Simple way to transpose columns and rows in SQL?
There are several ways that you can transform this data. In your original post, you stated that PIVOT
seems too complex for this scenario, but it can be applied very easily using both the UNPIVOT
and PIVOT
functions in SQL Server.
However, if you do not have access to those functions this can be replicated using UNION ALL
to UNPIVOT
and then an aggregate function with a CASE
statement to PIVOT
:
Create Table:
CREATE TABLE yourTable([color] varchar(5), [Paul] int, [John] int, [Tim] int, [Eric] int);
INSERT INTO yourTable
([color], [Paul], [John], [Tim], [Eric])
VALUES
('Red', 1, 5, 1, 3),
('Green', 8, 4, 3, 5),
('Blue', 2, 2, 9, 1);
Union All, Aggregate and CASE Version:
select name,
sum(case when color = 'Red' then value else 0 end) Red,
sum(case when color = 'Green' then value else 0 end) Green,
sum(case when color = 'Blue' then value else 0 end) Blue
from
(
select color, Paul value, 'Paul' name
from yourTable
union all
select color, John value, 'John' name
from yourTable
union all
select color, Tim value, 'Tim' name
from yourTable
union all
select color, Eric value, 'Eric' name
from yourTable
) src
group by name
See SQL Fiddle with Demo
The UNION ALL
performs the UNPIVOT
of the data by transforming the columns Paul, John, Tim, Eric
into separate rows. Then you apply the aggregate function sum()
with the case
statement to get the new columns for each color
.
Unpivot and Pivot Static Version:
Both the UNPIVOT
and PIVOT
functions in SQL server make this transformation much easier. If you know all of the values that you want to transform, you can hard-code them into a static version to get the result:
select name, [Red], [Green], [Blue]
from
(
select color, name, value
from yourtable
unpivot
(
value for name in (Paul, John, Tim, Eric)
) unpiv
) src
pivot
(
sum(value)
for color in ([Red], [Green], [Blue])
) piv
See SQL Fiddle with Demo
The inner query with the UNPIVOT
performs the same function as the UNION ALL
. It takes the list of columns and turns it into rows, the PIVOT
then performs the final transformation into columns.
Dynamic Pivot Version:
If you have an unknown number of columns (Paul, John, Tim, Eric
in your example) and then an unknown number of colors to transform you can use dynamic sql to generate the list to UNPIVOT
and then PIVOT
:
DECLARE @colsUnpivot AS NVARCHAR(MAX),
@query AS NVARCHAR(MAX),
@colsPivot as NVARCHAR(MAX)
select @colsUnpivot = stuff((select ','+quotename(C.name)
from sys.columns as C
where C.object_id = object_id('yourtable') and
C.name <> 'color'
for xml path('')), 1, 1, '')
select @colsPivot = STUFF((SELECT ','
+ quotename(color)
from yourtable t
FOR XML PATH(''), TYPE
).value('.', 'NVARCHAR(MAX)')
,1,1,'')
set @query
= 'select name, '+@colsPivot+'
from
(
select color, name, value
from yourtable
unpivot
(
value for name in ('+@colsUnpivot+')
) unpiv
) src
pivot
(
sum(value)
for color in ('+@colsPivot+')
) piv'
exec(@query)
See SQL Fiddle with Demo
The dynamic version queries both yourtable
and then the sys.columns
table to generate the list of items to UNPIVOT
and PIVOT
. This is then added to a query string to be executed. The plus of the dynamic version is if you have a changing list of colors
and/or names
this will generate the list at run-time.
All three queries will produce the same result:
| NAME | RED | GREEN | BLUE |
-----------------------------
| Eric | 3 | 5 | 1 |
| John | 5 | 4 | 2 |
| Paul | 1 | 8 | 2 |
| Tim | 1 | 3 | 9 |
Transpose columns to rows with ANSI sql
If you know you have four values, you can use conditional aggregation:
select max(case when seqnum = 1 then id end) as id_1,
max(case when seqnum = 2 then id end) as id_2,
max(case when seqnum = 3 then id end) as id_3,
max(case when seqnum = 4 then id end) as id_4
from (select t.*, row_number() over (order by id) as seqnum
from t
) t;
I'm not sure if this fits your requirements. If you are looking for something with a variable number of columns, then you need to use dynamic SQL.
How to transpose a query result in SQL Server (rows to columns)
PIVOT is the way to accomplish this and it can be confusing (at least it was to me) at first.
https://www.codeproject.com/Tips/500811/Simple-Way-To-Use-Pivot-In-SQL-Query
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