在c#或sql中，如何从具有不同条件的同一个表中获取公共数据

我有两个表，一个表由itemID和name列组成

另一个表是Location，其列为ItemID、LocationID 每个项目可以有多个位置 例如：我有3个项目鼠标，键盘，扬声器

• 鼠标位于4个位置-A、B、C、D
• 键盘有两个位置-A、C
• 扬声器位于3个位置-A、B、C

现在我想要一个c#或sql代码，它将为我提供当前示例中所有3项的公共位置，即a。

我想您需要：

select l.locationid
from locations l
group by l.locationid
having count(*) = (select count(*) from items);

这假设行在

位置中是唯一的。否则，请使用
计数（不同的项目ID）

是一个显示其工作原理的数据小提琴。
试试LINQ union：

int[] ints1 = { 5, 3, 9, 7, 5, 9, 3, 7 };
int[] ints2 = { 8, 3, 6, 4, 4, 9, 1, 0 };

IEnumerable<int> union = ints1.Union(ints2);

int[]ints1={5,3,9,7,5,9,3,7}；
int[]ints2={8,3,6,4,4,9,1,0}；
IEnumerable并集=ints1.union（ints2）；


你能试试这个吗
 您可以尝试在SQL Server中使用PIVOT，也许它对您有用

CREATE TABLE #items (
  ID_item int,
  name varchar(20)
)
CREATE TABLE #item_location (
  ID_item int,
  ID_location char(1)
)

INSERT INTO #items( ID_item, name ) VALUES (1,'Mouse')
INSERT INTO #items( ID_item, name ) VALUES (2,'Keyboard')
INSERT INTO #items( ID_item, name ) VALUES (3,'Speaker')

INSERT INTO #item_location (ID_item, ID_location) VALUES (1,'A')
INSERT INTO #item_location (ID_item, ID_location) VALUES (1,'B')
INSERT INTO #item_location (ID_item, ID_location) VALUES (1,'C')
INSERT INTO #item_location (ID_item, ID_location) VALUES (1,'D')
INSERT INTO #item_location (ID_item, ID_location) VALUES (2,'A')
INSERT INTO #item_location (ID_item, ID_location) VALUES (2,'C')
INSERT INTO #item_location (ID_item, ID_location) VALUES (3,'A')
INSERT INTO #item_location (ID_item, ID_location) VALUES (3,'B')
INSERT INTO #item_location (ID_item, ID_location) VALUES (3,'C')


--SELECT B.ID_location, COUNT(1) 
--FROM #items AS A
--INNER JOIN #item_location AS B ON A.ID_item = B.ID_Item
--GROUP BY B.ID_Location;

DECLARE @sql NVARCHAR(max);
DECLARE @columns VARCHAR(200);

SET @columns = STUFF(
     (
     SELECT
       ','+ QUOTENAME(LTRIM(name))
     FROM
       (SELECT DISTINCT
         A.name
        FROM #items AS A
       ) AS T 
     FOR XML PATH('')
     ), 1, 1, '')

 SET @sql = N'
  SELECT
   * 
  FROM
  (  
  SELECT  ID_location,name
  FROM #item_location A INNER JOIN #items B ON B.ID_item = A.ID_item 
  ) AS T
  PIVOT   
  (
  count(name)
  FOR name IN (' + @columns + N')
  ) AS P order by ID_location;'; 

 EXEC sp_executesql @sql;

  DROP TABLE #item_location
  DROP TABLE #items

搜索DTO（数据传输对象）@Sona。A和C都是这三个项目的共同点。关系划分总是那么有趣！因为RDBMS中几乎没有用于此的内置运算符。（或者我的技能过时了）他为什么要试试这个？@Sona。我添加了一个dbfiddle来显示它的工作原理。现在检查fiddle@Sona。如果您通过添加
WHERE
子句来更改逻辑，那么您应该期望中断代码。这回答了——并且正确地回答了——你提出的问题。如果您还有其他问题，请作为新问题提问。@Sona:Gordon是对的-但更具建设性的是，您的WHERE子句应该添加到两个selects to work中（在HAVING子句的内部和外部）@GordonLinoff对不起，我是堆栈新手，所以不知道它是如何工作的，我刚才给出了一个例子，上面查询的输出是ID\u location键盘鼠标扬声器-----------------------------------A 11 B 0 1 C 1 1 1 D 0 1 0，但我只想要所有items，在当前示例中是AOhh，我理解，您可以使用group by作为ID_位置，使用ORDER by作为comun位置的排名，如果有人想证明其他结果，我将代码复制到SQL fiddle，
CREATE TABLE #items (
  ID_item int,
  name varchar(20)
)
CREATE TABLE #item_location (
  ID_item int,
  ID_location char(1)
)

INSERT INTO #items( ID_item, name ) VALUES (1,'Mouse')
INSERT INTO #items( ID_item, name ) VALUES (2,'Keyboard')
INSERT INTO #items( ID_item, name ) VALUES (3,'Speaker')

INSERT INTO #item_location (ID_item, ID_location) VALUES (1,'A')
INSERT INTO #item_location (ID_item, ID_location) VALUES (1,'B')
INSERT INTO #item_location (ID_item, ID_location) VALUES (1,'C')
INSERT INTO #item_location (ID_item, ID_location) VALUES (1,'D')
INSERT INTO #item_location (ID_item, ID_location) VALUES (2,'A')
INSERT INTO #item_location (ID_item, ID_location) VALUES (2,'C')
INSERT INTO #item_location (ID_item, ID_location) VALUES (3,'A')
INSERT INTO #item_location (ID_item, ID_location) VALUES (3,'B')
INSERT INTO #item_location (ID_item, ID_location) VALUES (3,'C')


--SELECT B.ID_location, COUNT(1) 
--FROM #items AS A
--INNER JOIN #item_location AS B ON A.ID_item = B.ID_Item
--GROUP BY B.ID_Location;

DECLARE @sql NVARCHAR(max);
DECLARE @columns VARCHAR(200);

SET @columns = STUFF(
     (
     SELECT
       ','+ QUOTENAME(LTRIM(name))
     FROM
       (SELECT DISTINCT
         A.name
        FROM #items AS A
       ) AS T 
     FOR XML PATH('')
     ), 1, 1, '')

 SET @sql = N'
  SELECT
   * 
  FROM
  (  
  SELECT  ID_location,name
  FROM #item_location A INNER JOIN #items B ON B.ID_item = A.ID_item 
  ) AS T
  PIVOT   
  (
  count(name)
  FOR name IN (' + @columns + N')
  ) AS P order by ID_location;'; 

 EXEC sp_executesql @sql;

  DROP TABLE #item_location
  DROP TABLE #items