从 SQL Server 中的多个表中选择数据

Question

我有 6 个具有相同列 AFFECTED_ITEM 的唯一表。

我想要一个查询将为每个表输出列 AFFECTED_ITEM 和 Count(*)。

SELECT 
     AFFECTED_ITEM, Count(*)
FROM 
    dbo.Table1
WHERE 
    AFFECTED_ITEM IS NOT NULL
GROUP BY 
    AFFECTED_ITEM;

SELECT 
    AFFECTED_ITEM, Count(*)
FROM 
    dbo.Table2
WHERE 
    AFFECTED_ITEM IS NOT NULL
GROUP BY 
    AFFECTED_ITEM;

...

SELECT 
    AFFECTED_ITEM, Count(*)
FROM 
    dbo.Table6
WHERE 
    AFFECTED_ITEM IS NOT NULL
GROUP BY 
    AFFECTED_ITEM;

例子：

AFFECTED_ITEM | Table1 | Table2 | Table3 | Table6 |
--------------------------------------------------
Item1         |  53    |   45   |   12   |   0    |
Item2         |   4    |   13   |   77   |   9    |
Item3         |   7    |    0   |   24   |   23   |

等等。

Answer 1

使用Common Table Expression 从所有表中获取AFFECTED_ITEM 的所有可能值的列表：

WITH AffectedItems (AFFECTED_ITEM) AS (
  SELECT DISTINCT AFFECTED_ITEM  FROM table1
  UNION
  SELECT DISTINCT AFFECTED_ITEM  FROM table2
  UNION
  SELECT DISTINCT AFFECTED_ITEM   FROM table3
  UNION
  SELECT DISTINCT AFFECTED_ITEM   FROM table4
  UNION
  SELECT DISTINCT AFFECTED_ITEM   FROM table5
  UNION
  SELECT DISTINCT AFFECTED_ITEM   FROM table6
)

然后将其与Group By 子句结合LEFT Joins 以获取计数：

WITH AffectedItems (AFFECTED_ITEM) AS (
  SELECT DISTINCT AFFECTED_ITEM  FROM table1
  UNION
  SELECT DISTINCT AFFECTED_ITEM  FROM table2
  UNION
  SELECT DISTINCT AFFECTED_ITEM   FROM table3
  UNION
  SELECT DISTINCT AFFECTED_ITEM   FROM table4
  UNION
  SELECT DISTINCT AFFECTED_ITEM   FROM table5
  UNION
  SELECT DISTINCT AFFECTED_ITEM   FROM table6
)
SELECT ai.AFFECTED_ITEM, count(t1.name) as table1, count(t2.name) as table2, 
count(t3.name) as table3,count(t4.name) as table4, count(t5.name) as table5, 
count(t6.name) as table6
FROM AffectedItems ai
LEFT JOIN dbo.table1 t1 on t1.AFFECTED_ITEM = ai.AFFECTED_ITEM
LEFT JOIN dbo.table2 t2 on t2.AFFECTED_ITEM = ai.AFFECTED_ITEM
LEFT JOIN dbo.table3 t3 on t3.AFFECTED_ITEM = ai.AFFECTED_ITEM
LEFT JOIN dbo.table1 t4 on t4.AFFECTED_ITEM = ai.AFFECTED_ITEM
LEFT JOIN dbo.table2 t5 on t5.AFFECTED_ITEM = ai.AFFECTED_ITEM
LEFT JOIN dbo.table3 t6 on t6.AFFECTED_ITEM = ai.AFFECTED_ITEM
GROUP BY ai.AFFECTED_ITEM

在sql fiddle 中看到它的演示。

Answer 2

您可以在关键列中使用LEFT JOIN 和Count Distinct

SELECT t.AFFECTED_ITEM, 
    Count(DISTINCT t1.KeyId ) AS Table1,
    Count(DISTINCT t2.KeyId ) AS Table2,
    Count(DISTINCT t3.KeyId ) AS Table3,
    Count(DISTINCT t4.KeyId ) AS Table4,
    Count(DISTINCT t5.KeyId ) AS Table5,
    Count(DISTINCT t6.KeyId ) AS Table6

FROM yourTable t
LEFT JOIN Table1 t1 ON t.AFFECTED_ITEM = t1.AFFECTED_ITEM
LEFT JOIN Table2 t2 ON t.AFFECTED_ITEM = t2.AFFECTED_ITEM
LEFT JOIN Table3 t3 ON t.AFFECTED_ITEM = t3.AFFECTED_ITEM
LEFT JOIN Table4 t4 ON t.AFFECTED_ITEM = t4.AFFECTED_ITEM
LEFT JOIN Table5 t5 ON t.AFFECTED_ITEM = t5.AFFECTED_ITEM
LEFT JOIN Table6 t6 ON t.AFFECTED_ITEM = t6.AFFECTED_ITEM

GROUP BY t.AFFECTED_ITEM

Answer 3

左连接不是真正的 reault，您需要像这样 2×2 完全外连接：

with CteT1AndT2 as (
 SELECT  coalesce(t1.AFFECTED_ITEM,t2.AFFECTED_ITEM) as AFFECTED_ITEM, 
    Count(DISTINCT t1.KeyId ) AS CntTable1,
    Count(DISTINCT t2.KeyId ) AS CntTable2,

   FROM  Table1 t1 
     FULL OUTER JOIN Table2 ON t1.AFFECTED_ITEM = t2.AFFECTED_ITEM
    GROUP BY t1.AFFECTED_ITEM,t2.AFFECTED_ITEM
)

然后对接下来的 2 个表和接下来的两个表重复此操作，然后将所有结果完全连接在一起。这将是一个很长的查询，但您肯定不会丢失 ant 数据。

看看这个链接：http://www.dofactory.com/sql/full-outer-join 你需要完全连接，然后为了避免空值需要'coalesce'，左连接是绝对错误的，你会丢失右表中的数据。

Answer 4

首先将所有 table1 ， table2 ... table6 数据插入临时表。然后使用基于该临时表的 PIVOT 概念

  CREATE TABLE #table(AFFECTED_ITEM VARCHAR(100),_Count INT,_table 
  VARCHAR(100))

  INSERT INTO #table(AFFECTED_ITEM ,_Count , _table )
  SELECT AFFECTED_ITEM, Count(*),'Table1'
  FROM dbo.Table1
  WHERE AFFECTED_ITEM IS NOT NULL
  GROUP BY AFFECTED_ITEM 

  INSERT INTO #table(AFFECTED_ITEM ,_Count , _table )
  SELECT AFFECTED_ITEM, Count(*),'Table2'
  FROM dbo.Table2
  WHERE AFFECTED_ITEM IS NOT NULL
  GROUP BY AFFECTED_ITEM 

  .......  Upto table6 


  SELECT AFFECTED_ITEM , ISNULL([Table1],0) [Table1] , ISNULL([Table2],0) 
  [Table2] , ISNULL([Table3],0) [Table3] , ISNULL([Table4],0) [Table4] , 
  ISNULL([Table5],0) [Table5],ISNULL([Table6],0) [Table6]
  FROM 
  (
     SELECT AFFECTED_ITEM , _Count , _table     
     FROM #table
  ) A
  PIVOT
 (
   SUM(_Count) FOR _table IN ([Table1],[Table2],[Table3],[Table4],[Table5],
   [Table6])
 ) pvt 

Answer 5

请尝试以下...

SELECT itemCountFinder1.AFFECTED_ITEM AS AFFECTED_ITEM,
       COALESCE( itemCount1, 0 ) AS Table1,
       COALESCE( itemCount2, 0 ) AS Table2,
       COALESCE( itemCount3, 0 ) AS Table3,
       COALESCE( itemCount4, 0 ) AS Table4,
       COALESCE( itemCount5, 0 ) AS Table5,
       COALESCE( itemCount6, 0 ) AS Table6
FROM ( SELECT AFFECTED_ITEM,
              Count( * ) AS itemCount1
       FROM dbo.Table1
       WHERE AFFECTED_ITEM IS NOT NULL
       GROUP BY AFFECTED_ITEM ) AS itemCountFinder1
LEFT JOIN ( SELECT AFFECTED_ITEM,
                   Count( * ) AS  AS itemCount2
            FROM dbo.Table2
            WHERE AFFECTED_ITEM IS NOT NULL
            GROUP BY AFFECTED_ITEM ) AS itemCountFinder2 ON itemCountFinder1.AFFECTED_ITEM = itemCountFinder2.AFFECTED_ITEM
LEFT JOIN ( SELECT AFFECTED_ITEM,
                   Count( * ) AS itemCount3
            FROM dbo.Table3
            WHERE AFFECTED_ITEM IS NOT NULL
            GROUP BY AFFECTED_ITEM ) AS itemCountFinder3 ON itemCountFinder1.AFFECTED_ITEM = itemCountFinder3.AFFECTED_ITEM
LEFT JOIN ( SELECT AFFECTED_ITEM,
                   Count( * ) AS itemCount4
            FROM dbo.Table4
            WHERE AFFECTED_ITEM IS NOT NULL
            GROUP BY AFFECTED_ITEM ) AS itemCountFinder4 ON itemCountFinder1.AFFECTED_ITEM = itemCountFinder4.AFFECTED_ITEM
LEFT JOIN ( SELECT AFFECTED_ITEM,
                   Count( * ) AS itemCount5
            FROM dbo.Table5
            WHERE AFFECTED_ITEM IS NOT NULL
            GROUP BY AFFECTED_ITEM ) AS itemCountFinder5 ON itemCountFinder1.AFFECTED_ITEM = itemCountFinder5.AFFECTED_ITEM
LEFT JOIN ( SELECT AFFECTED_ITEM,
                   Count( * ) AS itemCount6
            FROM dbo.Table6
            WHERE AFFECTED_ITEM IS NOT NULL
            GROUP BY AFFECTED_ITEM ) AS itemCountFinder6 ON itemCountFinder1.AFFECTED_ITEM = itemCountFinder6.AFFECTED_ITEM

在这里，我们将您的六个查询返回的五个数据集与公共值 AFFECTED_ITEM 的第六个查询进行连接（在这种情况下，您执行此操作的顺序无关紧要）。

然后我们SELECT 来自新形成的数据集的每一行并显示每个计数字段。 Coalesce 用于显示0，其中AFFECTED_ITEM 的值不存在计数。

如果您有任何问题或cmets，请随时发表相应的评论。