Tsql SQL查询中的多重计数
给出以下简单的表格结构: 有没有一种不使用子查询(这很容易)的方法可以让我获得部门列表、每个部门的组数以及每个部门的库存数 示例输出:Tsql SQL查询中的多重计数,tsql,sql-server-2000,group-by,Tsql,Sql Server 2000,Group By,给出以下简单的表格结构: 有没有一种不使用子查询(这很容易)的方法可以让我获得部门列表、每个部门的组数以及每个部门的库存数 示例输出: DeptID DeptName GroupCount ItemCount ----------------------------------------------------- 1 Department 1 3 6 2 Department 2
DeptID DeptName GroupCount ItemCount
-----------------------------------------------------
1 Department 1 3 6
2 Department 2 1 1
3 Department 1 3 3
4 Department 4 1 1
我的直觉告诉我,这只是一个简单的问题,让小组的陈述正确,但到目前为止,我画了一个空白。如果它确实需要使用子查询,这不是问题。我只是想确认一下,以备将来参考
注意:使用SQL Server 2000解决此特定问题对不起,我没有坐在我的SQL Server前面。这是你的第一次尝试。我可能无法正确理解您期望的结果,但也许您可以将此作为起点
SELECT
Department.DeptId,
Department.DeptName,
Group.GroupId,
COUNT (Inventory.GroupId) as TotalItems
FROM
Department
INNER JOIN Groups
On (Department.DeptId = Groups.DeptId)
INNER JOIN Inventory
On (Inventory.GroupId = Groups.GroupId)
GROUP BY
Department.DeptId,
Department.DeptName
Group.GroupId,
Inventory.GroupId
以下至少是获得结果的一种方法
SELECT d.DeptID, d.DeptName, ISNULL(g.Groups, 0), ISNULL(t.TotalItems, 0)
FROM
Departments d
LEFT OUTER JOIN (
SELECT d.DeptID, Groups = COUNT(*)
FROM Departments d
INNER JOIN Groups g ON g.DeptID = d.DeptID
GROUP BY d.DeptID
) g ON g.DeptID = d.DeptID
LEFT OUTER JOIN (
SELECT d.DeptID, TotalItems = COUNT(*)
FROM Departments d
INNER JOIN Groups g ON g.DeptID = d.DeptID
INNER JOIN Inventory i ON i.GroupID = g.GroupID
GROUP BY d.DeptID
) t ON t.DeptID = d.DeptID
结果如下:
deptID Groups Items
----- ------ -----
1 3 6
2 1 1
3 3 3
4 1 1
这也将为没有组
或只有组
而没有项目的部门
生成正确的0
,以下是我的尝试
declare @Depatments table
(
DeptID int
,DeptName varchar(15)
)
declare @Groups table
(
GroupID int
,DeptID int
)
declare @Inventory table
(
ItemID int
,GroupID int
)
INSERT INTO @Depatments VALUES (1,'Department 1')
INSERT INTO @Depatments VALUES (2,'Department 2')
INSERT INTO @Depatments VALUES (3,'Department 3')
INSERT INTO @Depatments VALUES (4,'Department 4')
INSERT INTO @Groups VALUES (1,1)
INSERT INTO @Groups VALUES (2,1)
INSERT INTO @Groups VALUES (3,3)
INSERT INTO @Groups VALUES (4,4)
INSERT INTO @Groups VALUES (5,2)
INSERT INTO @Groups VALUES (6,3)
INSERT INTO @Groups VALUES (7,1)
INSERT INTO @Groups VALUES (8,3)
INSERT INTO @Inventory VALUES (1 ,2)
INSERT INTO @Inventory VALUES (2 ,3)
INSERT INTO @Inventory VALUES (3 ,8)
INSERT INTO @Inventory VALUES (4 ,1)
INSERT INTO @Inventory VALUES (5 ,4)
INSERT INTO @Inventory VALUES (6 ,5)
INSERT INTO @Inventory VALUES (7 ,1)
INSERT INTO @Inventory VALUES (8 ,2)
INSERT INTO @Inventory VALUES (9 ,2)
INSERT INTO @Inventory VALUES (10,3)
INSERT INTO @Inventory VALUES (11,7)
--works with derived tables
SELECT
d.DeptName,dt_g.CountOf AS GroupCount, dt_i.CountOf AS InventotyCount
FROM @Depatments d
LEFT OUTER JOIN (SELECT
COUNT(*) AS CountOf,DeptID
FROM @Groups
GROUP BY DeptID
) dt_g ON d.DeptID=dt_g.DeptID
LEFT OUTER JOIN (SELECT
COUNT(*) AS CountOf,g.DeptID
FROM @Groups g
INNER JOIN @Inventory i ON g.GroupID=i.GroupID
GROUP BY DeptID
) dt_i ON d.DeptID=dt_i.DeptID
@列文:谢谢你的标签编辑。我已经习惯于在2005年工作了,所以标记已经成为我的本能。@TheTXI:别提了。顺便说一句,我相信第二部门的组数和项目数应该是1?!为什么第二部门的组数是0?如果我完全搞砸了,我真的不会感到惊讶。这是使用完全随机的数据,所以我试图把数据加起来。如果有人发现算术中有错误,请随意编辑。我使用派生表方法和@Quassnoi query获得与@TheTXI相同的组总数。部门2有1个组,所以@Quassnoi,你的数据一定是错误的,你的查询给出了正确的值,查看我的答案,抓取我的表,插入并重试…在样本数据上,你的查询可以工作,但它会为没有组的部门选择noting。非常好。下次我将等到SQLExpress安装完成后再回答。笛卡尔连接在这里几乎是不可能的。很可能是组和部门之间的哈希连接,然后是结果集和项目之间的哈希连接。如果GroupID和DeptID是主键,那么结果集的行数将与Departments完全相同。是的,我的想法被搞砸了-我认为项目是加入到Departments,而不是组。Doh.great answer,但是使用COUNT(DISTINCT ISNULL(xxxxx,0))来消除警告:Null值被聚合或其他集合操作消除。对于没有组的部门,使用ISNULL将返回1而不是0对于没有组的部门,使用ISNULL将返回1而不是0。我最初试图用SUM来消除空值(如果为空,则为0,否则为1结束),但结果表明,仅仅计数更简单,警告实际上并不有害:)@Quassnoi,正确!我忘了它周围的COUNT()是如何计算0的!
deptID Groups Items
----- ------ -----
1 3 6
2 1 1
3 3 3
4 1 1
declare @Depatments table
(
DeptID int
,DeptName varchar(15)
)
declare @Groups table
(
GroupID int
,DeptID int
)
declare @Inventory table
(
ItemID int
,GroupID int
)
INSERT INTO @Depatments VALUES (1,'Department 1')
INSERT INTO @Depatments VALUES (2,'Department 2')
INSERT INTO @Depatments VALUES (3,'Department 3')
INSERT INTO @Depatments VALUES (4,'Department 4')
INSERT INTO @Groups VALUES (1,1)
INSERT INTO @Groups VALUES (2,1)
INSERT INTO @Groups VALUES (3,3)
INSERT INTO @Groups VALUES (4,4)
INSERT INTO @Groups VALUES (5,2)
INSERT INTO @Groups VALUES (6,3)
INSERT INTO @Groups VALUES (7,1)
INSERT INTO @Groups VALUES (8,3)
INSERT INTO @Inventory VALUES (1 ,2)
INSERT INTO @Inventory VALUES (2 ,3)
INSERT INTO @Inventory VALUES (3 ,8)
INSERT INTO @Inventory VALUES (4 ,1)
INSERT INTO @Inventory VALUES (5 ,4)
INSERT INTO @Inventory VALUES (6 ,5)
INSERT INTO @Inventory VALUES (7 ,1)
INSERT INTO @Inventory VALUES (8 ,2)
INSERT INTO @Inventory VALUES (9 ,2)
INSERT INTO @Inventory VALUES (10,3)
INSERT INTO @Inventory VALUES (11,7)
--works with derived tables
SELECT
d.DeptName,dt_g.CountOf AS GroupCount, dt_i.CountOf AS InventotyCount
FROM @Depatments d
LEFT OUTER JOIN (SELECT
COUNT(*) AS CountOf,DeptID
FROM @Groups
GROUP BY DeptID
) dt_g ON d.DeptID=dt_g.DeptID
LEFT OUTER JOIN (SELECT
COUNT(*) AS CountOf,g.DeptID
FROM @Groups g
INNER JOIN @Inventory i ON g.GroupID=i.GroupID
GROUP BY DeptID
) dt_i ON d.DeptID=dt_i.DeptID