Question

我不认为自己是一个完整的SQL新手，但我现在已经盯着这个问题两天了，打开和关闭，我开始想起我可能！

使用以下两个表：

ID    Category
1     Animal
2     Color
3     Sport

Name    ID    Value
Fred    1     Cat
Fred    2     Blue
Fred    3     Football
Sally   1     Dog
Sally   3     Jogging
James   2     Green
Anne    3     Swimming

我无法找到group by，sub-query，union，cte或pivot命令的任意组合，这些命令将从'（ID = 1或ID = 2）'查询返回的多行合并为不同的行有多列。

E.G：

where (ID=1 or ID=2)

Name     Animal    Color
Fred     Cat       Blue
Sally    Dog       NULL
James    NULL      Green

任何人都可以告诉我是否有一个有效的SQL解决方案，或者我是否在报告中应该由代码处理的事情上浪费时间？

由于

Answer 1

这是PIVOT语法

SELECT Name,[1] as Animal, [2] as Color
FROM
(SELECT Name,Id,Value
    FROM Table) AS SourceTable
PIVOT
(
MIN(Value)
FOR Id IN ([1], [2])
) AS PivotTable;

Answer 2

你可以用：

Select a.Name as Name, a.Value as Animal, c.Value as Color
 FROM
     (SELECT Name, Value 
        FROM table2 INNER JOIN table1 
             ON table2.ID = table1.ID AND table2.ID =1) as a 
     LEFT JOIN 
     (SELECT Name, Value 
        FROM table2 INNER JOIN table1 
          ON table2.ID = table1.ID AND table2.ID =2) as c
     ON a.Name = c.Name
UNION
Select c.Name as Name, a.Value as Animal, c.Value as Color
 FROM
     (SELECT Name, Value 
        FROM table2 INNER JOIN table1 
             ON table2.ID = table1.ID AND table2.ID =1) as a 
     RIGHT JOIN 
     (SELECT Name, Value 
        FROM table2 INNER JOIN table1 
          ON table2.ID = table1.ID AND table2.ID =2) as c
     ON a.Name = c.Name

表2很奇怪，设计不是很好。

Answer 3

WITH filtered_table AS (
  SELECT Name, ID, Value
  FROM table2
  WHERE ID IN (1, 2)
)
SELECT
  t2.Name,
  Animal = MAX(CASE t1.ID WHEN 1 THEN ft.Value END),
  Color  = MAX(CASE t1.ID WHEN 2 THEN ft.Value END)
FROM (SELECT DISTINCT Name FROM filtered_table) t2
  INNER JOIN table1 t1 ON t1.ID IN (1, 2)
  LEFT JOIN filtered_table ft ON t2.Name = ft.Name AND t1.ID = ft.ID
GROUP BY t2.Name

查询将多行合并为具有多列的不同行

3 个答案: