SQL - query for combining multiple rows - sql

Question

I'm searching but i can't find a solution for my problem.
I've a table (say T1) with this data:
SampleCode
Name
Content
#
1
A#
#
2
B#
#
3
C#
#
1
A#
#
2
B#
#
3
C#
So i need a select query resulting in :
Column 1
Column 2
Column 3
SampleCode
#
#
Name.1
A#
A#
Name.2
B#
B#
Name.3
C#
C#
Does anyone has an hint?
Thanks
Fabio

Answer 1

Check out the 2 options in this article: https://www.sqlshack.com/multiple-options-to-transposing-rows-into-columns/
If using TSQL, you could use a TRANSPOSE statement. Or you can create the result set using cursors/loops and dynamic SQL.
Fully Dynamic Solution
I can't believe I hammered this out... maybe I did it just to see if I could. It's long and complicated and uses several loops. I think you should re-evaluate what you're trying to do. This can't be run in a view. You would have to put into a function or stored procedure. You may want to evaluate the temp table names to see if they are compatible with your environment. Also, since the temp table name are not unique, you cannot run multiple instances; if you want to run multiple instances, you would have to add a unique identifier to a column in the temp tables or to temp table names. This is fully dynamic... you don't have to know how many columns you need ahead of time.
--**************************************************
--Header area... sample data and temp tables.
--**************************************************
--Clean up sample and result tables if they exist.
IF OBJECT_ID(N'tempdb..#T1') IS NOT NULL
DROP TABLE #T1;
IF OBJECT_ID(N'tempdb..#ResultsTemp') IS NOT NULL
DROP TABLE #ResultsTemp;
IF OBJECT_ID(N'tempdb..#codeTable') IS NOT NULL
DROP TABLE #codeTable;
--For Debugging.
DECLARE #debug int = 1; --0=no debug, 1=show debug messages, do not exec all SQL statements.
--Table var to hold sample data.
CREATE TABLE #T1 (
SampleCode nvarchar(50),
[Name] nvarchar(50),
Content nvarchar(50),
row_num int
);
--Load Sample Data.
INSERT INTO #T1 (SampleCode, [Name], Content)
VALUES
('#', '1', 'A#')
, ('#', '2', 'B#')
, ('#', '3', 'C#')
, ('#', '1', 'A#')
, ('#', '2', 'B#')
, ('#', '3', 'C#')
;
--**********END HEADER**********
--Number the rows so we can loop over them.
UPDATE #T1
SET row_num = newT1.row_num
FROM
(
SELECT t12.SampleCode
, t12.[Name]
, T12.Content
, ROW_NUMBER()OVER(ORDER BY SampleCode, [Name], Content) as row_num
FROM #T1 as t12
) AS newT1
WHERE #T1.SampleCode = newT1.SampleCode
AND #T1.[Name] = newT1.[Name]
AND #T1.Content = newT1.Content
;
SELECT * FROM #T1; --Debugging... just show the contents of #T1 after adding row_num
--Create temp table to load results.
CREATE TABLE #ResultsTemp (
Column1 nvarchar(50)
);
--Create some variable to track looping (without a cursor).
DECLARE #loopCount int = 1;
DECLARE #maxLoops int = (SELECT COUNT(DISTINCT SampleCode) FROM #T1);
DECLARE #sql nvarchar(512);
--Add columns to #ResultsTable dynamically
WHILE (#loopCount <= (#maxLoops))
BEGIN
SET #sql = 'ALTER TABLE #ResultsTemp ADD ' + QUOTENAME('Column' + CAST((#loopCount + 1) as nvarchar)) + ' nvarchar(50) NULL';
IF (#debug = 1) PRINT #sql;
EXEC (#sql);
SET #loopCount = #loopCount + 1;
END
--************************************************************
--SECTION FOR INSERTING FIRST ROW for "SampleCode"
--************************************************************
--Vars for tracking the SampleCode variations processed.
DECLARE #sampleLoop int = 1;
DECLARE #sampleCount int = (SELECT COUNT(DISTINCT SampleCode) FROM #T1);
CREATE TABLE #codeTable (
SampleCode nvarchar(50)
, row_num int
);
--Create a list of unique SampleCodes to loop over.
INSERT INTO #codeTable (SampleCode)
SELECT DISTINCT
SampleCode
FROM #T1;
UPDATE #codeTable
SET row_num = newCT.row_num
FROM
(
SELECT ct2.SampleCode
, ROW_NUMBER()OVER(ORDER BY SampleCode) as row_num
FROM #codeTable as ct2
) AS newCT
WHERE #codeTable.SampleCode = newCT.SampleCode
;
SET #sql = 'INSERT INTO #ResultsTemp (Column1) SELECT ''SampleCode''';
IF (#debug = 1) PRINT #sql;
EXEC (#sql);
WHILE (#sampleLoop <= #sampleCount)
BEGIN
SET #sql = 'UPDATE #ResultsTemp SET Column' + CAST(#SampleLoop + 1 as nvarchar) + '=(SELECT TOP 1 SampleCode FROM #codeTable WHERE row_num = ' + CAST(#sampleLoop as nvarchar) + ');';
IF (#debug = 1) PRINT #sql;
EXEC (#sql);
SET #sampleLoop = #sampleLoop + 1;
END
IF (#debug = 1) SELECT * FROM #ResultsTemp;
--**********END SECTION**********
--**************************************************
--SECTION FOR INSERTING THE REST OF THE CONTENT DATA
--**************************************************
--Vars for tracking number of rows processed from T1.
SET #loopCount = 1;
SET #maxLoops = (SELECT MAX(row_num) FROM #T1);
--Loop over each row in T1.
WHILE (#loopCount <= #maxLoops)
BEGIN
--Create a name for this row.
DECLARE #nameRaw nvarchar(50) = (SELECT TOP 1 [Name] FROM #T1 WHERE row_num = #loopCount);
DECLARE #codeNum nvarchar(50) = (
SELECT TOP 1 ct.row_num
FROM #T1 as t
INNER JOIN #codeTable as ct
ON ct.SampleCode = t.SampleCode
WHERE t.row_num = #loopCount);
DECLARE #name nvarchar(50) = 'Name.' + #nameRaw;
--First insert a row for this Name... if not already in the list.
SET #sql = 'INSERT INTO #ResultsTemp (Column1)
SELECT ''Name.'' + t.[Name]
FROM #T1 as t
LEFT OUTER JOIN #ResultsTemp as rt
ON rt.Column1 = ''' + #name + '''
WHERE t.row_num = ' + CAST(#loopCount as nvarchar) + '
AND rt.Column1 IS NULL;';
IF (#debug = 1) PRINT #sql;
EXEC (#sql);
--Update this Name row with the "content".
SET #sql = 'UPDATE rt
SET Column' + CAST(#codeNum + 1 as nvarchar) + '=t.Content
FROM #ResultsTemp as rt
INNER JOIN #T1 as t
ON t.row_num = ' + CAST(#loopCount as nvarchar) + '
AND t.[Name] = ''' + #nameRaw + '''
WHERE rt.Column1 = ''' + #name + ''';';
IF (#debug = 1) PRINT #sql;
EXEC (#sql);
SET #loopCount = #loopCount + 1;
END
--Show everything in the temp Results table.
SELECT *
FROM #ResultsTemp;
Result Set:
Static Select Solution
This next option is not dynamic. You have to know how many columns you need and then you can copy the "Column3" code to any new columns. You have to change the column name and update the "Select TOP 1" statement as commented for each new column you would copy.
WITH CodeTable AS (
SELECT DISTINCT t.SampleCode
FROM #T1 as t
)
SELECT DISTINCT
'Name.' + [Name]
, (
SELECT TOP 1 Content
FROM #T1 as t2
WHERE t2.SampleCode = (
SELECT TOP 1 SampleCode
FROM CodeTable as ct
ORDER BY SampleCode
)
AND t2.[Name] = t.[Name]
) as Column2
, (
SELECT TOP 1 Content
FROM #T1 as t2
WHERE t2.SampleCode = (
SELECT TOP 1 SampleCode
FROM CodeTable as ct
WHERE ct.SampleCode NOT IN (
SELECT TOP 1 SampleCode --Update the TOP 1 to be TOP [number of previous columns]
FROM CodeTable as ct2
ORDER BY ct2.SampleCode
)
ORDER BY ct.SampleCode
)
AND t2.[Name] = t.[Name]
) as Column3
FROM #T1 as t
Static PivotTable Solution
This solution is from the link I posted. Again, you have to know the number of columns you need and it doesn't have generic column names like you specify. But, it is another solution if you reconsider your output.
--Use PivotTable.
SELECT *
FROM
(
SELECT [Name], Content
FROM #T1
) AS SourceTable PIVOT(MAX(Content) FOR [Content] IN([A#],
[A#]
)) AS PivotTable;

Answer 2

Pivot table can solve your prooblem:
DECLARE #T TABLE (SampleCode sysname, Name sysname, Content sysname)
INSERT #T (SampleCode, Name, Content)
VALUES
('#', '1', 'A#'),
('#', '2', 'B#'),
('#', '3', 'C#'),
('#', '1', 'A#'),
('#', '2', 'B#'),
('#', '3', 'C#')
SELECT CONCAT('Name.', PIVOTTABLE.Name), [#], [#]
FROM
(
SELECT * FROM #T AS t
) AS SOURCE
PIVOT (
MAX(Content)
FOR SampleCode IN ([#], [#])
) AS PIVOTTABLE
Of course this is the solution for what you provided in the question.
When the columns are too many to manually write down then use Dynamic query and the only parts needed to be generate is the values in FOR expression and the same value in SELECT