Question

我在将Sample表中的Sample_Measure_FK连接到Measurement Table时遇到问题。

代码部分是：

create table Sample
(
  Site_ID       varchar2(5) not null,
  Recorded_On timestamp not null,
  Scientist_Num varchar2(7) not null,
  Comments      varchar2(4000), -- or CLOB

  constraint Sample_PK primary key (Site_ID, Recorded_On),
  constraint Sample_Site_FK foreign key (Site_ID) references Site,
  constraint Sample_Scientist_FK foreign key (Scientist_Num) references Scientist(Scientist_Num),
  -- the following is the problem:
  constraint Sample_Measure_FK foreign key (Recorded_On) references Measurement(Recorded_On)
);

create table Measurement
(
  Site_ID varchar2(5) not null,
  Recorded_On timestamp not null,
  Name varchar2(50),
  Value numeric(10,8),
  Outlier_Indicator varchar2(50),

  constraint Measurement_PK primary key(Site_ID, Recorded_On),

);

我收到的错误消息是：

Error starting at line : 65 in command -
create table Sample
(
  Site_ID       varchar2(5) not null,
  Recorded_On timestamp not null,
  Scientist_Num varchar2(7) not null,
  Comments      varchar2(4000), -- or CLOB

  constraint Sample_PK primary key (Site_ID, Recorded_On),
  constraint Sample_Site_FK foreign key (Site_ID) references Site,
  constraint Sample_Scientist_FK foreign key (Scientist_Num) references Scientist(Scientist_Num),
  constraint Sample_Measure_FK foreign key (Recorded_On) references Measurement(Recorded_On)
)
Error report -
SQL Error: ORA-02270: no matching unique or primary key for this column-list
02270. 00000 -  "no matching unique or primary key for this column-list"
*Cause:    A REFERENCES clause in a CREATE/ALTER TABLE statement
           gives a column-list for which there is no matching unique or primary
           key constraint in the referenced table.
*Action:   Find the correct column names using the ALL_CONS_COLUMNS
           catalog view

其他外键可以使用，但粗体的外键不起作用。

Answer 1

需要在Measurement表

之前创建Sample表

验证外键，因此引用的表必须已存在。

外键需要指向另一个表的主键

约束Sample_Measure_FK外键（Recorded_On）引用Measurement（Recorded_On）

好吧，Recorded_on不是Measurement的主键。或者它也可以是一个独特的约束，但它也不是。

您通常将外键指向其他表的主键。

Answer 2

也许这是命名，但我希望单个样本有多个测量值，这表明外键关系在错误的表上：

create table Sample (
  Site_ID       varchar2(5) not null,
  Recorded_On timestamp not null,
  Scientist_Num varchar2(7) not null,
  Comments      varchar2(4000), -- or CLOB

  constraint Sample_PK primary key (Site_ID, Recorded_On)
  constraint Sample_Site_FK foreign key (Site_ID) references Site,
  constraint Sample_Scientist_FK foreign key (Scientist_Num) references Scientist(Scientist_Num)
);


create table Measurement (
  Site_ID varchar2(5) not null,
  Recorded_On timestamp not null,
  Name varchar2(50),
  Value numeric(10, 8),
  Outlier_Indicator varchar2(50),

  constraint Measurement_Sample_FK foreign key (Site_ID, Recorded_On) references Sample(Site_ID, Recorded_On),

  constraint Measurement_PK primary key (Site_ID, Recorded_On, Name)
);

This does work.

ORA-02270外键，无法找到错误

2 个答案: