concatenate and de-dupe multiple rows - sql

Question

I have some incoming rows in the below format.
| Col1 | Col2 | Col3 |
| 1 | A | 1 |
| 1 | A | 1,2 |
| 1 | A | 1,3 |
| 1 | A | 2,4 |
Desired outputsql is
| Col1 | Col2 | Col3 |
| 1 | A | 1,2,3,4 |
Basically, group all rows based on Col1 and Col2 and then concatenate and remove duplicates from Col3.
SELECT COL1, COL2, {?????}
FROM TABLEA
GROUP BY COL1, COL2;
I could not think much at this moment. Any pointers would be much appreciated. I am inclined to WX2 database, but any ANSI compliant snippet would be helpful.

Answer 1

For Postgres use this:
select col1, col2, string_agg(distinct col3, ',') as col3
from (
select col1, col2, x.col3
from tablea, unnest(string_to_array(col3, ',')) as x(col3)
) t
group by col1, col2;
This is largely ANSI compliant except for the string_to_array() and string_agg() function.

Answer 2

You could try with transpose or concatenation functions. The difficulty comes from the fact that col3 is varchar and a conversion is needed to get the distinct values.
With MySQL :
SELECT col1, col2, GROUP_CONCAT(DISTINCT col3) AS col3 FROM
(SELECT col1, col2, CONVERT(SUBSTR(col3, 1), UNSIGNED INTEGER) AS col3 FROM (
SELECT 1 AS col1, 'A' AS col2, '1' AS col3 UNION ALL
SELECT 1 AS col1, 'A' AS col2, '1,2' AS col3 UNION ALL
SELECT 1 AS col1, 'A' AS col2, '1,3' AS col3 UNION ALL
SELECT 1 AS col1, 'A' AS col2, '2,4' AS col3
) AS t
UNION ALL
SELECT col1, col2, CONVERT(SUBSTR(col3, 3), UNSIGNED INTEGER) AS col3 FROM (
SELECT 1 AS col1, 'A' AS col2, '1' AS col3 UNION ALL
SELECT 1 AS col1, 'A' AS col2, '1,2' AS col3 UNION ALL
SELECT 1 AS col1, 'A' AS col2, '1,3' AS col3 UNION ALL
SELECT 1 AS col1, 'A' AS col2, '2,4' AS col3
) AS t1
) AS t2
WHERE col3 <> 0
Result :
col1 | col2 | col3
1 | A | 1,2,3,4

Answer 3

For SQL Server: first concatenate all col3 values using STUFF method and INSERT INTO CTE table.Based on this CTE tables split all rows as individual into single column based on CTE table.Finally concate all DISTINCT strings with help of STUFF.
CREATE TABLE #table ( Col1 INT , Col2 VARCHAR(10) , Col3 VARCHAR(10))
INSERT INTO #table ( Col1 , Col2 , Col3 )
SELECT 1 , 'A' , '1' UNION ALL
SELECT 1 , 'A' , '1,2' UNION ALL
SELECT 1 , 'A' , '1,3' UNION ALL
SELECT 1 , 'A' , '2,4'
;WITH CTEValues ( Colval ) AS
(
SELECT STUFF ( ( SELECT ',' + Col3 FROM #table T2 WHERE T2.Col2 =
T1.col2 FOR XML PATH('') ),1,1,'')
FROM #table T1
GROUP BY Col2
)
SELECT * INTO #CTEValues
FROM CTEValues
;WITH CTEDistinct ( SplitValues , SplitRemain ) AS
(
SELECT SUBSTRING(Colval,0,CHARINDEX(',',Colval)),
SUBSTRING(Colval,CHARINDEX(',',Colval)+1,LEN(Colval))
FROM #CTEValues
UNION ALL
SELECT CASE WHEN CHARINDEX(',',SplitRemain) = 0 THEN SplitRemain ELSE
SUBSTRING(SplitRemain,0,CHARINDEX(',',SplitRemain)) END,
CASE WHEN CHARINDEX(',',SplitRemain) = 0 THEN '' ELSE
SUBSTRING(SplitRemain,CHARINDEX(',',SplitRemain)+1,LEN(SplitRemain))
END
FROM CTEDistinct
WHERE SplitRemain <> ''
)
SELECT STUFF ( ( SELECT DISTINCT ',' + SplitValues FROM CTEDistinct T2
FOR XML PATH('') ),1,1,'')