[英]Select rows in one table, based on column values in another table?
我需要为另一个表中的每个匹配行 select 一列。 听起来很简单,但有一个转折点。
我在下面的代码工作得很好,这正是我想要它做的。 但是我必须硬编码到要查找的部门的查询中。 我希望它根据在“部门”表中找到的部门代码进行子选择,而不是要求我对该公司可能存在的每个可能的部门进行硬编码。
我需要 select 根据 DepartmentsStatus 表中定义的公司存在的部门,从 DepartmentStatus 匹配部门状态。
我怀疑这是一张 pivot 表,但它们比我的水平高一点。
(公司表)
Company_ID Company_Name
-------------------------
1 Home Office
2 Stanton Office
3 NYC Office
(部门表)
CompanyID Department_Code
----------------------------
1 Sales
1 Inventory
1 Retail
1 Maint
2 OtherDept
2 ThatDept
2 BobsDept
(部门状态表)
Company_ID Department StatusCode
-----------------------------------------
1 Sales InReview
1 Inventory InReview
1 Retail Ready
1 Maint Done
2 OtherDept InReview
2 ThatDept Research
2 BobsDept InReview
注意:我使用“TOP 1”,即使 Company_ID+Department 上有唯一索引,所以匹配的行永远不会超过一个。
因此,对于 Company_ID=1:
select Company_ID,
(select top 1 StatusCode from DepartmentStatus ds where ds.Company_ID = cm.Company_ID and ds.Department='Sales') as SalesStatus
(select top 1 StatusCode from DepartmentStatus ds where ds.Company_ID = cm.Company_ID and ds.Department='Inventory') as InvStatus
(select top 1 StatusCode from DepartmentStatus ds where ds.Company_ID = cm.Company_ID and ds.Department='Retail') as RetailStatus
(select top 1 StatusCode from DepartmentStatus ds where ds.Company_ID = cm.Company_ID and ds.Department='Main') as MaintStatus
from Company cm
Where cm.CompanyID=1
结果:
Company_ID SalesStatus InvStatus RetailStatus MaintStatus
--------------- --------------- ---------- ------------- ------------
1 InReview InReview Ready Done
或者,对于 CompanyID=2:
select Company_ID,
(select top 1 StatusCode from DepartmentStatus ds where ds.CompanyID = cm.Company_ID and ds.Department='OtherDept') as OtherDeptStatus
(select top 1 StatusCode from DepartmentStatus ds where ds.CompanyID = cm.Company_ID and ds.Department='ThatDept') as ThatDeptStatus
(select top 1 StatusCode from DepartmentStatus ds where ds.CompanyID = cm.Company_ID and ds.Department='BobsDept') as BobsDeptStatus
from Company cm
Where cm.CompanyID=2
结果:
Company_ID OtherDeptStatus ThatDeptStatus BobsDeptStatus
---------- ---------------- -------------- --------------
2 InReview Research InReview
因此,对于公司 1,我需要 go 获取部门销售、库存、零售和维护的状态。 但是对于公司 2,我需要获取 Departments OtherDept、ThatDept 和 BobsDept 的状态。
我认为描述我正在尝试做的步骤是:
问题是,我不知道提前(在查询时)每个公司存在哪些部门,所以我需要根据每个公司实际存在的部门进行子选择。
已经有一些其他 SO 答案与我所要求的很接近,建议使用 JOIN 来完成此操作,但是,它们都假设您在编写 join 语句时提前知道要查询的值.
我正在寻找解决此问题的方法,而不仅仅是对我当前尝试的更正。 如果您对如何实现这一点有更好的想法,我很乐意看到它。
您似乎正在寻找条件聚合。 使用这种技术,您的查询可以简化如下,以避免需要多个内联子查询:
select Company_ID,
max(case when ds.Department='Sales' then ds.StatusCode end) as SalesStatus,
max(case when ds.Department='Inventory' then ds.StatusCode end) as InvStatus,
max(case when ds.Department='Retail' then ds.StatusCode end) as RetailStatus,
max(case when ds.Department='Main' then ds.StatusCode end) as MaintStatus
from
Company cm
inner join DepartmentStatus ds on ds.Company_ID = cm.Company_ID
Where cm.CompanyID=1
group by cm.CompanyID
这将是我(未经测试的)穴居人解决问题的方法。 您唯一需要提前知道的是,您所在的公司有多少个不同的部门,部门最多。
DROP TABLE IF EXISTS Iddepartmentstatus;
DECLARE @Result TABLE(
Companyid INT,
Department1 NVARCHAR(MAX),
Department2 NVARCHAR(MAX),
Department3 NVARCHAR(MAX),
Department4 NVARCHAR(MAX),
Department5 NVARCHAR(MAX));
CREATE TABLE Iddepartmentstatus(
Num INT IDENTITY(1, 1),
Department NVARCHAR(MAX),
Statuscode NVARCHAR(MAX));
DECLARE @IDCompany TABLE(
Num INT IDENTITY(1, 1),
Companyid INT,
Companyname NVARCHAR(MAX));
INSERT INTO @IDCompany (Companyid,
Companyname)
SELECT Company_Id,
Company_Name
FROM Company;
DECLARE @Departmentcount INT = 0,
@Departmentstatuscount INT = 0,
@Companycount INT = 0;
WHILE @Companycount <=
(
SELECT MAX(Num)
FROM @IDCompany)
BEGIN
INSERT INTO Iddepartmentstatus (Department,
Statuscode)
SELECT Department,
Statuscode
FROM Departmentstatus
WHERE Company_Id = @Companycount;
INSERT INTO @Result (Companyid)
SELECT @Companycount AS T;
INSERT INTO @Result (Department1)
SELECT IIF(1 <=
(
SELECT MAX(Num)
FROM @IDCompany), Department + ': ' + Departmentstatus, NULL)
FROM Iddepartmentstatus
WHERE Num = 1;
INSERT INTO @Result (Department2)
SELECT IIF(2 <=
(
SELECT MAX(Num)
FROM @IDCompany), Department + ': ' + Departmentstatus, NULL)
FROM Iddepartmentstatus
WHERE Num = 2;
INSERT INTO @Result (Department3)
SELECT IIF(3 <=
(
SELECT MAX(Num)
FROM @IDCompany), Department + ': ' + Departmentstatus, NULL)
FROM Iddepartmentstatus
WHERE Num = 3;
INSERT INTO @Result (Department4)
SELECT IIF(4 <=
(
SELECT MAX(Num)
FROM @IDCompany), Department + ': ' + Departmentstatus, NULL)
FROM Iddepartmentstatus
WHERE Num = 4;
INSERT INTO @Result (Department5)
SELECT IIF(5 <=
(
SELECT MAX(Num)
FROM @IDCompany), Department + ': ' + Departmentstatus, NULL)
FROM Iddepartmentstatus
WHERE Num = 5;
TRUNCATE TABLE Iddepartmentstatus;
SET @Companycount = @Companycount + 1;
END;
DROP TABLE IF EXISTS Iddepartmentstatus;
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