Sql 使用case语句将多行合并到一个列中

我必须用逗号分隔的值连接一列，这些值分布在多行中。 根据行号，我必须对文本列进行编码。 例如，对于第2行，文本列中的值应为AB、BC

Name    Date    Identifier  Text              Row_num        Val
Charles 08/07/18      30565     AB                  1         2
Charles 08/07/18      30565     AB,BC               2         4
Charles 08/07/18      30565     AB,BC,CD                3         6
Charles 08/07/18      30565     AB,BC,CD,EF         4         3
Charles 08/07/18      30565     AB,BC,CD,EF,FG      5         4
Charles 08/07/18      30565     AB,BC,CD,EF,FG,GF   7         5

输入

Name    Date    Identifier  Text              Row_num        Val
Charles 08/07/18      30565     AB                  1         2
Charles 08/07/18      30565     AB,BC               2         4
Charles 08/07/18      30565     AB,BC,CD                3         6
Charles 08/07/18      30565     AB,BC,CD,EF         4         3
Charles 08/07/18      30565     AB,BC,CD,EF,FG      5         4
Charles 08/07/18      30565     AB,BC,CD,EF,FG,GF   7         5

所需输出：

Name    Date    Identifier  Text              Row_num        Val
Charles 08/07/18      30565     AB                  1         2
Charles 08/07/18      30565     AB,BC               2         4
Charles 08/07/18      30565     AB,BC,CD                3         6
Charles 08/07/18      30565     AB,BC,CD,EF         4         3
Charles 08/07/18      30565     AB,BC,CD,EF,FG      5         4
Charles 08/07/18      30565     AB,BC,CD,EF,FG,GF   7         5

使用的查询：

Name    Date    Identifier  Text              Row_num        Val
Charles 08/07/18      30565     AB                  1         2
Charles 08/07/18      30565     AB,BC               2         4
Charles 08/07/18      30565     AB,BC,CD                3         6
Charles 08/07/18      30565     AB,BC,CD,EF         4         3
Charles 08/07/18      30565     AB,BC,CD,EF,FG      5         4
Charles 08/07/18      30565     AB,BC,CD,EF,FG,GF   7         5

SELECT 
    Name,
    Date,
    ,Identifier
    MAX(CASE WHEN Row_nnum = 1 THEN Text END)  ||
    MAX(CASE WHEN Row_nnum = 2  THEN ', ' || Text ELSE '' END) ||
    MAX(CASE WHEN Row_nnum = 3  THEN ', ' || Text ELSE '' END) ||
    MAX(CASE WHEN Row_nnum = 4  THEN ', ' || Text ELSE '' END) ||
    MAX(CASE WHEN Row_nnum = 5  THEN ', ' || Text ELSE '' END) ||
    MAX(CASE WHEN Row_nnum = 6  THEN ', ' || Text ELSE '' END) ||
    MAX(CASE WHEN Row_nnum = 7  THEN ', ' || Text ELSE '' END)
    SUM(val)
FROM TABLE 
GROUP BY 1,2,3;

此查询的问题是，它在第2、3、4、5、7行的文本列中提供空值。因此无法获得所需的输出

Name    Date    Identifier  Text              Row_num        Val
Charles 08/07/18      30565     AB                  1         2
Charles 08/07/18      30565     AB,BC               2         4
Charles 08/07/18      30565     AB,BC,CD                3         6
Charles 08/07/18      30565     AB,BC,CD,EF         4         3
Charles 08/07/18      30565     AB,BC,CD,EF,FG      5         4
Charles 08/07/18      30565     AB,BC,CD,EF,FG,GF   7         5

SELECT 
    Name,
    Date,
    ,Identifier
    MAX(CASE WHEN Row_nnum = 1 THEN Text END)  ||
    MAX(CASE WHEN Row_nnum = 2  THEN ', ' || Text ELSE '' END) ||
    MAX(CASE WHEN Row_nnum = 3  THEN ', ' || Text ELSE '' END) ||
    MAX(CASE WHEN Row_nnum = 4  THEN ', ' || Text ELSE '' END) ||
    MAX(CASE WHEN Row_nnum = 5  THEN ', ' || Text ELSE '' END) ||
    MAX(CASE WHEN Row_nnum = 6  THEN ', ' || Text ELSE '' END) ||
    MAX(CASE WHEN Row_nnum = 7  THEN ', ' || Text ELSE '' END),
    SUM(val)
FROM TABLE 
GROUP BY 1,2,3;

---

只需将该条件添加到

案例中

：

Name    Date    Identifier  Text              Row_num        Val
Charles 08/07/18      30565     AB                  1         2
Charles 08/07/18      30565     AB,BC               2         4
Charles 08/07/18      30565     AB,BC,CD                3         6
Charles 08/07/18      30565     AB,BC,CD,EF         4         3
Charles 08/07/18      30565     AB,BC,CD,EF,FG      5         4
Charles 08/07/18      30565     AB,BC,CD,EF,FG,GF   7         5

SELECT Name, Date, Identifier,
       (MAX(CASE WHEN Row_nnum = 1 THEN Text END)  ||
        MAX(CASE WHEN Row_nnum = 2 AND Text IS NOT NULL THEN ', ' || Text ELSE '' END) ||
        MAX(CASE WHEN Row_nnum = 3 AND Text IS NOT NULL THEN ', ' || Text ELSE '' END) ||
        MAX(CASE WHEN Row_nnum = 4 AND Text IS NOT NULL THEN ', ' || Text ELSE '' END) ||
        MAX(CASE WHEN Row_nnum = 5 AND Text IS NOT NULL THEN ', ' || Text ELSE '' END) ||
        MAX(CASE WHEN Row_nnum = 6 AND Text IS NOT NULL THEN ', ' || Text ELSE '' END) ||
        MAX(CASE WHEN Row_nnum = 7 AND Text IS NOT NULL THEN ', ' || Text ELSE '' END)
       ),
      SUM(val)
FROM TABLE 
GROUP BY 1, 2, 3;

---

请注意，OP似乎无法使用agg_concatenate.No，这不会有帮助。这给出了相同的结果，因为for row_num case语句将再次处理数据，而不是从派生列（row_num=1）获取数据。