sql - 如何在 SQL 中的单行内连接多行？

Question

如何使用 SQL 将多行连接成单行？我的数据库是 DB2

TableFoo
 -------
 Id      Name
 1       Apples
 1       Tomatoes
 1       Potatoes
 2       Banana
 2       Peach

我想要类似的东西

ID       FruitsAvailable
-------------------------
 1       Apples, Tomatoes, Potatoes

Answer 1

试试这个

  SELECT id ,FruitsAvailable 
  FROM
      (SELECT id , group_concat(Name) as FruitsAvailable 
       FROM  TableFoo
       WHERE id = 1) t

这里演示 SQLFIDDLE

编辑：在 db2 中你需要创建函数然后调用它

 CREATE FUNCTION MySchema/MyUDF (
PARCol2 CHAR(5) )
RETURNS VARCHAR(1024)   
LANGUAGE SQL 
NOT DETERMINISTIC 
READS SQL DATA 
CALLED ON NULL INPUT 
DISALLOW PARALLEL 

 BEGIN 
  DECLARE ReturnVal VARCHAR(1024) NOT NULL DEFAULT '';

  FOR CsrC1 AS C1 CURSOR 
      FOR SELECT MyCol1 
             FROM MyTable 
             WHERE MyCol2 = ParCol2 
      DO SET ReturnVal = ReturnVal Concat CsrC1.MyCol1; 
  END FOR; 

  RETURN LTRIM(ReturnVal); 
 END  ; 

然后在这里调用

     Select  id, MyUDF(Name) as FruitsAvailable
     From TableFoo 
     where id = 1 

Answer 2

使用此查询：

SELECT Id, GROUP_CONCAT(Name SEPARATOR ', ') FROM TableFoo GROUP BY Id;