跨多个表的SQL外键
我是模特儿。检查表单是任意的,本质上是字段列表跨多个表的SQL外键,sql,sql-server,foreign-keys,Sql,Sql Server,Foreign Keys,我是模特儿。检查表单是任意的,本质上是字段列表 CREATE TABLE InspectionForms ( InspectionFormId INT PRIMARY KEY, InspectionFormName NVARCHAR(64), ... (CreatorId, TimeCreated, etc.) ); CREATE TABLE InspectionFormFields ( InspectionFormId INT FOREIGN KEY REFE
CREATE TABLE InspectionForms
(
InspectionFormId INT PRIMARY KEY,
InspectionFormName NVARCHAR(64),
... (CreatorId, TimeCreated, etc.)
);
CREATE TABLE InspectionFormFields
(
InspectionFormId INT FOREIGN KEY REFERENCES InspectionForms,
InspectionFormFieldId INT,
FieldName NVARCHAR(64),
PRIMARY KEY(InspectionFormId, InspectionFormFieldId)
);
因此,使用名为浴室
的检查表单,以及厕所
、淋浴
和地板
的字段,我们的值如下所示:
InspectionForms
---------------
0 Bathroom
InspectionFormFields
--------------------
0 0 Toilet
0 1 Shower
0 2 Floor
CREATE TABLE InspectionValues
(
InspectionId INT FOREIGN KEY REFERENCES Inspections,
InspectionFormId INT FOREIGN KEY REFERENCES InspectionForms,
InspectionFormFieldId INT,
Rating TINYINT NOT NULL,
PRIMARY KEY(InspectionId, InspectionFormId, InspectionFormFieldId),
FOREIGN KEY(InspectionFormId, InspectionFormFieldId) REFERENCES InspectionFormFields
);
然后是实际完成的检查:
CREATE TABLE Inspections
(
InspectionId INT PRIMARY KEY,
InspectionFormId INT FOREIGN KEY REFERENCES InspectionForms,
... (InspectorId, TimeOfInspection, etc.)
);
CREATE TABLE InspectionValues
(
InspectionId INT FOREIGN KEY REFERENCES Inspections,
InspectionFormFieldId INT,
Rating TINYINT NOT NULL,
PRIMARY KEY(InspectionId, InspectionFormFieldId)
);
以下是一些示例值:
Inspections
-----------
0 0 ...
InspectionValues
----------------
0 0 5 (Inspection 0 scored a 5 in the Toilet)
0 1 3 (Inspection 0 scored a 3 in the Shower)
0 2 4 (Inspection 0 scored a 4 in the Floor)
关键是:我希望检查值
有一个外键
引用检查表单字段
。但是它没有InspectionFormId
列。我可以想出两种理论上的解决方案,但我不知道如何实现这两种方案
解决方案1:我可以简单地将检查表单
列从检查
移动到检查值
,然后添加外键。这将使我们的桌子看起来像这样:
InspectionForms
---------------
0 Bathroom
InspectionFormFields
--------------------
0 0 Toilet
0 1 Shower
0 2 Floor
CREATE TABLE InspectionValues
(
InspectionId INT FOREIGN KEY REFERENCES Inspections,
InspectionFormId INT FOREIGN KEY REFERENCES InspectionForms,
InspectionFormFieldId INT,
Rating TINYINT NOT NULL,
PRIMARY KEY(InspectionId, InspectionFormId, InspectionFormFieldId),
FOREIGN KEY(InspectionFormId, InspectionFormFieldId) REFERENCES InspectionFormFields
);
如果我这样做,我想以某种方式强制所有具有给定InspectionId
的inspectionvalue
共享InspectionFormId
的公共值(即,我不希望检查
跨越多个InspectionForms
)。一种简单有效的方法是确保每次更新时,此查询不会返回任何行:
SELECT InspectionId
FROM InspectionValues a
GROUP BY InspectionId
HAVING MIN(InspectionFormId) < MAX(InspectionFormId);
我使用的是SQL Server 2014,不需要支持任何其他版本的SQL。在这里正确的做法是什么?您应该在检查表中保留检查表单ID(而不是按照您的建议移动它)。由于InspectionId是主键,因此每个InspectionId不能只有一个inspectionformid
CREATE TABLE Inspections
(
InspectionId INT PRIMARY KEY,
InspectionFormId INT FOREIGN KEY REFERENCES InspectionForms,
);
然后将inspectionformid添加到inspectionvalues表中:
CREATE TABLE InspectionValues
(
InspectionId INT FOREIGN KEY REFERENCES Inspections,
InspectionFormId INT,
InspectionFormFieldId INT,
Rating TINYINT NOT NULL,
PRIMARY KEY(InspectionId, InspectionFormId, InspectionFormFieldId),
FOREIGN KEY(InspectionFormId, InspectionFormFieldId)
REFERENCES InspectionFormFields(InspectionFormId, InspectionFormFieldId)
))
在上面的解决方案1中,InspectionValues有两个包含InspectionFormId的外键,但您只需要如上所示的多列键。是什么强制要求
检查
和检查值
表中的检查Formid
列共享值,给定一个通用的检查ID
?现在,您甚至不需要检查表。然而,若您添加一个字段,如TimeOfInspection或Inspector,那个么您将需要该表。在任何情况下,为了回答您的问题,插入数据的应用程序都需要确保inspectionid在Inspections表和InspectionValues表之间匹配。@TimCooke:在检查中可以添加唯一的(inspectionid,InspectionFormId)
。然后从InspectionValues
到Inspections
的引用将采用外键(InspectionId,InspectionFormId)引用Inspections(InspectionId,InspectionFormId)
@AndiryM:这正是我要找的!非常感谢@AndriyM检查ID是检查的主键,因此在(检查ID,检查FormID)上添加唯一键是多余的,不必要的