[英]concatenate and de-dupe multiple rows
我有以下格式的一些傳入行。
| Col1 | Col2 | Col3 |
| 1 | A | 1 |
| 1 | A | 1,2 |
| 1 | A | 1,3 |
| 1 | A | 2,4 |
所需的outputsql是
| Col1 | Col2 | Col3 |
| 1 | A | 1,2,3,4 |
基本上,基於Col1和Col2對所有行進行分組,然后連接並從Col3中刪除重復項。
SELECT COL1, COL2, {?????}
FROM TABLEA
GROUP BY COL1, COL2;
我現在不能想太多。 任何指針將不勝感激。 我傾向於WX2數據庫,但任何符合ANSI的代碼段都將有所幫助。
對於SQL Server:首先使用STUFF方法和INSERT INTO CTE表連接所有col3值。基於此CTE表,基於CTE表將所有行單獨分割為單列。最后借助STUFF連接所有DISTINCT字符串。
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,'')
您可以嘗試使用轉置或串聯功能。 困難來自於這樣的事實,即col3是varchar,需要進行轉換才能獲得不同的值。 使用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
結果:
col1 | col2 | col3
1 | A | 1,2,3,4
對於Postgres,請使用以下命令:
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;
除了string_to_array()
和string_agg()
函數外,這基本上符合ANSI。
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