Foreign Key Constraint in oracle

问题

I have two tables Cal and EEL I want to use the primary key of cal that is Cal_id as the foreign key for EEl

Here's what I tried.

Create table ELL 
  (course_code varcahr2(10) Constraints pk_course_code Primary Key, 
    Course_Title varchar2(30),
    cal2_idnumber not null,
     Constraint fk_cal2 Foreign Key (cal_id) References cal_id(cal2_id)
)

but it shows error at line 6 Ora-00904 "Cal_ID" invalid character

can someone tell me how to do this

回答1:

ALTER TABLE table_name
add CONSTRAINT constraint_name
  FOREIGN KEY (column1, column2, ... column_n)
  REFERENCES parent_table (column1, column2, ... column_n);

回答2:

Not difficult, here below an example:

CREATE TABLE supplier
(   supplier_id     numeric(10)     not null,
    supplier_name   varchar2(50)    not null,
    contact_name    varchar2(50),   
    CONSTRAINT supplier_pk PRIMARY KEY (supplier_id)
);


CREATE TABLE products
(   product_id  numeric(10)     not null,
    supplier_id     numeric(10)     not null,
    CONSTRAINT fk_supplier
    FOREIGN KEY (supplier_id)
    REFERENCES supplier(supplier_id)
);

回答3:

References cal_id(cal2_id) -- call_id is not your table name.

Instead of above code you can use as below.

References parent_table_name(cal2_id)

回答4:

Constraint fk_cal_id2 Foreign Key (cal2_id) References cal(cal_id) ----------- constraint name (col in EEL) parent table name(parent table column name)

来源：https://stackoverflow.com/questions/9604099/foreign-key-constraint-in-oracle