[英]SQL Server 2005 - Query Help
I am trying to write a query using the following example tables:我正在尝试使用以下示例表编写查询:
Company公司
CompanyRelation公司关系
CompanySpecialty公司专业
The CompanyRelation
table is used because each company can have many subcompanies under it and each subcompany can have many companies over it.使用CompanyRelation
表是因为每个公司可以在其下拥有许多子公司,并且每个子公司可以在其上拥有许多公司。
Ideally, what I want to be able to find is all companies by a certain county and/or by a certain specialty.理想情况下,我希望能够找到某个县和/或某个专业的所有公司。 Now, normally, I would just join Company
to CompanySpecialty
and filter on those two fields, but here is where it gets tricky: the subcompanies don't have counties assigned to them, so if I filter on the county, all the subcompanies will be excluded.现在,通常情况下,我只需将Company
加入CompanySpecialty
并过滤这两个字段,但这就是棘手的地方:子公司没有分配给他们的县,所以如果我过滤县,所有子公司都将是排除。
If I filter the companies down to a county, I would like to display all subcompanies that are associated to that company, regardless of the fact that the subcompany does not have an address.如果我将公司过滤到一个县,我想显示与该公司关联的所有子公司,不管子公司没有地址。
To get around this, I have to bring in the CompanyRelation
table.为了解决这个问题,我必须引入CompanyRelation
表。
Example data:示例数据:
CompanyID---Name---County
1-----------ABC----King
2-----------BCD----Pierce
3-----------DEF----NULL
4-----------EFG----NULL
ParentCompanyID---ChildCompanyID
1-----------------1
1-----------------3
2-----------------2
2-----------------4
CompanyID---Specialty
1-----------Vehicles
2-----------Vehicles
3-----------Vehicles
4-----------Vehicles
Using this data, say I want to find all companies in King county that deal with vehicles.使用这些数据,假设我想找到金县所有经营车辆的公司。 In my results, I would expect to see Company 1 and Company 3.在我的结果中,我希望看到公司 1 和公司 3。
How can I write a query to accomplish this?我怎样才能写一个查询来完成这个?
The Diagram would be like this (with Company being the primary / parent table, and all others depending on it):图表将是这样的(公司是主/父表,所有其他表都依赖于它):
Company Specialty <-- Company <-- Relationship <-- Company --> Company Specialty公司专业 <-- 公司 <-- 关系 <--公司--> 公司专业
Converting it to SQL would be like this:将其转换为 SQL 将是这样的:
SELECT
--whatever fields you want, as long as you prefix with the table alias (p., ps., dr., c., cs.)
FROM
Company Parent P --parent
Left Join CompanySpecialty PS
ON P.CompanyID = PS.CompanyID
Left Join CompanyRelation CR
ON P.CompanyID = CR.ParentCompanyID
Left Join Company C
ON CR.ChildCompanyID = C.ComapnyID
Left Join Company Specialty CS
ON C.CompanyID = CS.CompanyID
WHERE
(PS.Specialty = 'Vehicle' AND P.County = 'King')
OR
(CS.Specialty = 'Vehicle' AND C.County = 'King')
SELECT
d.ChildCompanyID,
c.Name
FROM
CompanyRelation d
INNER JOIN
Company m
ON d.ParentCompanyID = m.CompanyID
INNER JOIN
CompanySpecialty s
ON d.ChildCompanyID = s.CompanyID
INNER JOIN
Company c
ON d.ChildCompanyID = c.CompanyID
WHERE
m.County = N'King'
AND s.Specialty = N'Vehicles'
Here is the sample that works:这是有效的示例:
create table #Company (
CompanyID int,
Name nvarchar(20),
County nvarchar(20))
GO
create table #CompanyRelation (
ParentCompanyID int,
ChildCompanyID int)
GO
create table #CompanySpecialty (
CompanyID int,
Specialty nvarchar(20))
GO
insert #Company VALUES (1, 'ABC', 'King');
insert #Company VALUES (2, 'DFG', NULL);
insert #Company VALUES (3, 'HIJ', NULL);
insert #Company VALUES (4, 'KLM', NULL);
GO
insert #CompanyRelation VALUES (1, 1);
insert #CompanyRelation VALUES (1, 3);
insert #CompanyRelation VALUES (2, 2);
insert #CompanyRelation VALUES (2, 4);
GO
insert #CompanySpecialty VALUES (1, 'Vehicles');
insert #CompanySpecialty VALUES (2, 'Vehicles');
insert #CompanySpecialty VALUES (3, 'Vehicles');
insert #CompanySpecialty VALUES (4, 'Vehicles');
GO
SELECT
d.ChildCompanyID,
c.Name
FROM
#CompanyRelation d
INNER JOIN
#Company m
ON d.ParentCompanyID = m.CompanyID
INNER JOIN
#CompanySpecialty s
ON d.ChildCompanyID = s.CompanyID
INNER JOIN
#Company c
ON d.ChildCompanyID = c.CompanyID
WHERE
m.County = N'King'
AND s.Specialty = N'Vehicles'
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