sql server - making a result vertical to horizontal [duplicate] - sql

Question

Apart from writing the cursor reading each rows and populating it into columns, any other alternative if I need to transpose each rows into columns ?
TimeSeconds TagID Value
1378700244 A1 3.75
1378700245 A1 30
1378700304 A1 1.2
1378700305 A2 56
1378700344 A2 11
1378700345 A3 0.53
1378700364 A1 4
1378700365 A1 14.5
1378700384 A1 144
1378700384 A4 10
The number of columns are not fixed.
Output : I just assigned n/a as a placeholder for no data in that intersection.
TimeSec A1 A2 A3 A4
1378700244 3.75 n/a n/a n/a
1378700245 30 n/a n/a n/a
1378700304 1.2 n/a n/a n/a
1378700305 n/a 56 n/a n/a
1378700344 n/a 11 n/a n/a
1378700345 n/a n/a 0.53 n/a
1378700364 n/a n/a n/a 4
1378700365 14.5 n/a n/a n/a
1378700384 144 n/a n/a 10
Hope you can share with me some tips. Thanks.

Answer 1

One way to do it if tagID values are known upfront is to use conditional aggregation
SELECT TimeSeconds,
COALESCE(MAX(CASE WHEN TagID = 'A1' THEN Value END), 'n/a') A1,
COALESCE(MAX(CASE WHEN TagID = 'A2' THEN Value END), 'n/a') A2,
COALESCE(MAX(CASE WHEN TagID = 'A3' THEN Value END), 'n/a') A3,
COALESCE(MAX(CASE WHEN TagID = 'A4' THEN Value END), 'n/a') A4
FROM table1
GROUP BY TimeSeconds
or if you're OK with NULL values instead of 'n/a'
SELECT TimeSeconds,
MAX(CASE WHEN TagID = 'A1' THEN Value END) A1,
MAX(CASE WHEN TagID = 'A2' THEN Value END) A2,
MAX(CASE WHEN TagID = 'A3' THEN Value END) A3,
MAX(CASE WHEN TagID = 'A4' THEN Value END) A4
FROM table1
GROUP BY TimeSeconds
or with PIVOT
SELECT TimeSeconds, A1, A2, A3, A4
FROM
(
SELECT TimeSeconds, TagID, Value
FROM table1
) s
PIVOT
(
MAX(Value) FOR TagID IN (A1, A2, A3, A4)
) p
Output (with NULLs):
TimeSeconds A1 A2 A3 A4
----------- ------- ------ ----- -----
1378700244 3.75 NULL NULL NULL
1378700245 30.00 NULL NULL NULL
1378700304 1.20 NULL NULL NULL
1378700305 NULL 56.00 NULL NULL
1378700344 NULL 11.00 NULL NULL
1378700345 NULL NULL 0.53 NULL
1378700364 4.00 NULL NULL NULL
1378700365 14.50 NULL NULL NULL
1378700384 144.00 NULL NULL 10.00
If you have to figure TagID values out dynamically then use dynamic SQL
DECLARE #cols NVARCHAR(MAX), #sql NVARCHAR(MAX)
SET #cols = STUFF((SELECT DISTINCT ',' + QUOTENAME(TagID)
FROM Table1
ORDER BY 1
FOR XML PATH(''), TYPE
).value('.', 'NVARCHAR(MAX)'),1,1,'')
SET #sql = 'SELECT TimeSeconds, ' + #cols + '
FROM
(
SELECT TimeSeconds, TagID, Value
FROM table1
) s
PIVOT
(
MAX(Value) FOR TagID IN (' + #cols + ')
) p'
EXECUTE(#sql)

Answer 2

SQL Server has a PIVOT command that might be what you are looking for.
select * from Tag
pivot (MAX(Value) for TagID in ([A1],[A2],[A3],[A4])) as TagTime;
If the columns are not constant, you'll have to combine this with some dynamic SQL.
DECLARE #columns AS VARCHAR(MAX);
DECLARE #sql AS VARCHAR(MAX);
select #columns = substring((Select DISTINCT ',' + QUOTENAME(TagID) FROM Tag FOR XML PATH ('')),2, 1000);
SELECT #sql =
'SELECT *
FROM TAG
PIVOT
(
MAX(Value)
FOR TagID IN( ' + #columns + ' )) as TagTime;';
execute(#sql);

Answer 3

Another option that may be suitable in this situation is using XML
The XML option to transposing rows into columns is basically an optimal version of the PIVOT in that it addresses the dynamic column limitation. 
The XML version of the script addresses this limitation by using a combination of XML Path, dynamic T-SQL and some built-in functions (i.e. STUFF, QUOTENAME).
Vertical expansion
Similar to the PIVOT and the Cursor, newly added policies are able to be retrieved in the XML version of the script without altering the original script.
Horizontal expansion
Unlike the PIVOT, newly added documents can be displayed without altering the script.
Performance breakdown
In terms of IO, the statistics of the XML version of the script is almost similar to the PIVOT – the only difference is that the XML has a second scan of dtTranspose table but this time from a logical read – data cache.
You can find some more about these solutions (including some actual T-SQL exmaples) in this article:
https://www.sqlshack.com/multiple-options-to-transposing-rows-into-columns/

Answer 4

Based on the solution from bluefeet here is a stored procedure that uses dynamic sql to generate the transposed table. It requires that all the fields are numeric except for the transposed column (the column that will be the header in the resulting table):
/****** Object: StoredProcedure [dbo].[SQLTranspose] Script Date: 11/10/2015 7:08:02 PM ******/
SET ANSI_NULLS ON
GO
SET QUOTED_IDENTIFIER ON
GO
-- =============================================
-- Author: Paco Zarate
-- Create date: 2015-11-10
-- Description: SQLTranspose dynamically changes a table to show rows as headers. It needs that all the values are numeric except for the field using for transposing.
-- Parameters: #TableName - Table to transpose
-- #FieldNameTranspose - Column that will be the new headers
-- Usage: exec SQLTranspose <table>, <FieldToTranspose>
-- table and FIeldToTranspose should be written using single quotes
-- =============================================
ALTER PROCEDURE [dbo].[SQLTranspose]
-- Add the parameters for the stored procedure here
#TableName NVarchar(MAX) = '',
#FieldNameTranspose NVarchar(MAX) = ''
AS
BEGIN
-- SET NOCOUNT ON added to prevent extra result sets from
-- interfering with SELECT statements.
SET NOCOUNT ON;
DECLARE #colsUnpivot AS NVARCHAR(MAX),
#query AS NVARCHAR(MAX),
#queryPivot AS NVARCHAR(MAX),
#colsPivot as NVARCHAR(MAX),
#columnToPivot as NVARCHAR(MAX),
#tableToPivot as NVARCHAR(MAX),
#colsResult as xml
select #tableToPivot = #TableName;
select #columnToPivot = #FieldNameTranspose
select #colsUnpivot = stuff((select ','+quotename(C.name)
from sys.columns as C
where C.object_id = object_id(#tableToPivot) and
C.name <> #columnToPivot
for xml path('')), 1, 1, '')
set #queryPivot = 'SELECT #colsResult = (SELECT '',''
+ quotename('+#columnToPivot+')
from '+#tableToPivot+' t
where '+#columnToPivot+' <> ''''
FOR XML PATH(''''), TYPE)'
exec sp_executesql #queryPivot, N'#colsResult xml out', #colsResult out
select #colsPivot = STUFF(#colsResult.value('.', 'NVARCHAR(MAX)'),1,1,'')
set #query
= 'select name, rowid, '+#colsPivot+'
from
(
select '+#columnToPivot+' , name, value, ROW_NUMBER() over (partition by '+#columnToPivot+' order by '+#columnToPivot+') as rowid
from '+#tableToPivot+'
unpivot
(
value for name in ('+#colsUnpivot+')
) unpiv
) src
pivot
(
sum(value)
for '+#columnToPivot+' in ('+#colsPivot+')
) piv
order by rowid'
exec(#query)
END

Answer 5

I had a slightly different requirement, whereby I had to selectively transpose columns into rows.
The table had columns:
create table tbl (ID, PreviousX, PreviousY, CurrentX, CurrentY)
I needed columns for Previous and Current, and rows for X and Y. A Cartesian product generated on a static table worked nicely, eg:
select
ID,
max(case when metric='X' then PreviousX
case when metric='Y' then PreviousY end) as Previous,
max(case when metric='X' then CurrentX
case when metric='Y' then CurrentY end) as Current
from tbl inner join
/* Cartesian product - transpose by repeating row and
picking appropriate metric column for period */
( VALUES (1, 'X'), (2, 'Y')) AS x (sort, metric) ON 1=1
group by ID
order by ID, sort