I addressed in class that the 2 foreign keys in the FlightData table are Depart_Code and Ariv_Code that there isn't any table to make references to them being a primary key in, in the relational schema we were given.
In class I was told that they reference Airport_Code in the Airport table. I was wondering I would go about doing that? I feel like I am missing something obvious. I appreciate any help offered I am still new to database in general and I am currently on Oracle 11g.
Airport table
CREATE TABLE Airport
(
Airport_Code VARCHAR2(7) CONSTRAINT pk_Airport Primary Key,
City_Code VARCHAR2(3),
CONSTRAINT fk_Airport_City_Code
FOREIGN KEY(City_Code) REFERENCES City,
Airport_Name VARCHAR2(30)
);
FlightData table:
CREATE TABLE FlightData
(
Flt_Nbr VARCHAR2(3) CONSTRAINT pk_FlightData Primary Key,
Depart_Code VARCHAR2(30),
Ariv_Code VARCHAR2(30)
);
To make sure Depart_Code and Ariv_Code always reference an airport in the Airport table you need to:
Make these columns NOT NULL.
Ensure they have the same data type as the key in Airport. Make them have a length of 7.
Add two foreign key constraints, each one based on each column.
For example, the second table could look like:
CREATE TABLE FlightData (
Flt_Nbr VARCHAR2(3) CONSTRAINT pk_FlightData Primary Key,
Depart_Code VARCHAR2(7) not null,
constraint fk1 foreign key (Depart_Code) references Airport (Airport_Code),
Ariv_Code VARCHAR2(7) not null,
constraint fk2 foreign key (Ariv_Code) references Airport (Airport_Code)
);
Related
I am learning how to create a small and simple database for class with Primary Key and Foreign Key restraints. I am getting ORA-02770 when attempting to run my ALTER TABLE statement, which as I understand is notifying me that the column I am referencing in the outside table is not listed as a primary key constraint. However, from what I can see my syntax is correct naming the primary keys in my CREATE TABLES statements. I searched inside the all_cons_columns table for the player_info table and it showed the primary keys listed as well. Could I get some guidance? Listed below is my current script:
CREATE TABLE Player_Game
( school varchar2(30),
player_number number(2,0),
game_number number(1,0),
CONSTRAINT playergame_pk PRIMARY KEY (school, player_number,game_number)
);
CREATE TABLE School
( school varchar2(30),
city varchar2(30),
coach varchar2(30),
team_name varchar2(30),
win_record number (2,0),
loss_record number (2,0),
CONSTRAINT school_pk PRIMARY KEY (school)
);
CREATE TABLE Game
( school varchar2(30),
game_number number(1,0),
game_date DATE,
game_score varchar2(15),
CONSTRAINT game_pk PRIMARY KEY (school, game_number)
);
CREATE TABLE player_info
( school varchar2(30),
player_number number(2,0),
player_name varchar2(25),
CONSTRAINT playerinfo_pk PRIMARY KEY (school, player_number)
);
CREATE TABLE city
( city varchar2(30),
population number(5,0),
CONSTRAINT city_pk PRIMARY KEY (city)
);
/*Here is the failing alter command */
ALTER TABLE Player_Game
ADD CONSTRAINT playergame_fk FOREIGN KEY (school) REFERENCES game(school);
You have incorrect column list in playergame_fk in the alter table statement. The column list of the foreign key must exactly match with the column list of the primary key it is referencing to.
Primary Key column list is school, game_number, therefore, your foreign key must have the same columns:
ALTER TABLE Player_Game
ADD CONSTRAINT playergame_fk FOREIGN KEY (school, game_number)
REFERENCES game(school, game_number);
I have a question on an exam that i don't know how to solve.
this is the question:
How do you keep the integrity of a 1-1 or 1-0 relationship between 2 tables?
Now a primary key and foreign key wouldn't work because then you can have a 1-m relationship. Maybe you can use unique in some way or alternative key?
We need to give the create table expressions and explain why this would work.
Here's an example of a 1-1 relationship in PostgreSQL. It requires the standard SQL feature of deferrable constraints:
create table employee (
id int primary key not null,
name varchar(20),
desk_id int not null,
constraint uq1 unique (desk_id),
constraint fk1 foreign key (desk_id) references desk (id)
deferrable initially immediate
);
create table desk (
id int primary key not null,
desk_code varchar(20).
employee_id int not null,
constraint uq2 unique (employee_id),
constraint fk2 foreign key (employee_id) references employee (id)
deferrable initially immediate
);
In simple English: every row of employee points to a desk. Every desk points to an employee.
Deferrable constraints are only implemented in PostgreSQL and Oracle, as far as I know.
I am going to give example from oracle
Here is 1:1 relationship example
create table state
(
sid number(3) ,
name varchar2(100),
gid number(3) not null,
constraint state_pk primary key (sid),
constraint gov_state_fk foreign key (gid) references gov(gid)
);
Here is 1:0..1 relationship (a.k.a. Surjection)
create table state
(
sid number(3) ,
name varchar2(100),
gid number(3) ,
constraint state_pk primary key (sid),
constraint gov_state_fk foreign key (gid) references gov(gid)
);
basicly what differs is,
In 1:0 relationship gid can be nullable
In 1:0..1 relationship gid cannot be null
EDIT: I also added Unicity for preserving 1:0..1 and 1:1 relationship.
I'm getting an error from oracle that says "number of referencing columns must match referenced columns."
I want my column recorded_on in the table measurement to reference recorded_on in the table called sample
The column Recorded on in the Sample table must be part of a composite key together with Scientist_Num
The error is coming from
FOREIGN KEY (Recorded_On) REFERENCES Sample(Scientist, Recorded_On, Site_ID)
CREATE TABLE Sample (
Scientist_Num varchar2(5) not null,
Recorded_On date not null,
Site_ID varchar2(4) not null,
Comments clob,
Primary key (Scientist_Num, Recorded_On),
FOREIGN KEY (Scientist_Num) REFERENCES Scientist(Scientist_Num),
FOREIGN KEY (Site_ID) REFERENCES Site(Site_ID)
);
CREATE TABLE Measurement (
Site_ID varchar2(4) not null,
Recorded_On date not null,
Name varchar2(10) not null,
Value varchar2(10),
Outlier_Indicator varchar2(10),
Primary key (Site_ID, Recorded_On, Name),
FOREIGN KEY (Site_ID) REFERENCES Sample(Site_ID),
FOREIGN KEY (Recorded_On) REFERENCES Sample(Scientist, Recorded_On, Site_ID)
);
The Scientist_Num and Recorded_On columns must be in a composite key together.
The answer to my problem and an explanation of what went wrong would be greatly appreciated.
You can create virtual column in sample table:
Recorded_virtual varchar2(5) [GENERATED ALWAYS] AS
(Scientist||Recorded_On||Site_ID) [VIRTUAL]
And create reference to this column:
CONSTRAINT fk_column
FOREIGN KEY (Recorded_On)
REFERENCES Sample(Recorded_virtual )
Foreign key references need to match the primary keys in number and type. So I think you intend:
CREATE TABLE Measurement (
Site_ID varchar2(4) not null,
Scientist_Num varchar2(5) not null,
----^ added for foreign key reference
Recorded_On date not null,
Name varchar2(10) not null,
Value varchar2(10),
Outlier_Indicator varchar2(10),
Primary key (Site_ID, Recorded_On, Name),
FOREIGN KEY (Site_ID) REFERENCES Site(Site_ID),
-------------------------------------^ Presumably you intend the site table
FOREIGN KEY (Scientist_Num, Recorded_On) REFERENCES
Sample(Scientist_Num, Recorded_On)
-----------------^ two columns, both need to already be defined
);
I suspect there are other issues with your data model, but this should fix the syntax error. If you want further help, then ask another question.
I am pretty new to SQL and I have a problem. I want to make a recursive relationship (a table that relates to itself), but I get an error when I try to execute my code. It's working fine without the Coordinator_Office_ID foreign key.
The error is:
The number of columns in the foreign-key referencing list is not equal
to the number of columns in the referenced list.
Create table Logistican (
Office_ID Number(10) Constraint nb_office Not NULL,
Worker_ID Number(15) Constraint lg_worker not null,
Name_logistican Varchar(20),
Room Varchar(10) constraint log_room UNIQUE,
Coordinator_Office_ID Integer,
Primary key (Office_ID, Worker_ID),
Constraint work_id Foreign key (Worker_ID) References worker(worker_ID) on delete cascade,
Constraint lg_cord_id Foreign key (Coordinator_Office_ID) References Logistican(Office_ID)
);
Yes, that's cause you have defined composite primary key like Primary key (Office_ID, Worker_ID) and thus your FK should include both of them else it will result in PFD (partial functional dependency)
Add the constraint with alter table:
Create table Logistican (
Office_ID Number(10) Constraint nb_office Not NULL,
Worker_ID Number(15) Constraint lg_worker not null,
Name_logistican Varchar(20),
Room Varchar(10) constraint log_room UNIQUE,
Coordinator_Office_ID Integer,
Primary key (Office_ID, Worker_ID),
Constraint work_id Foreign key (Worker_ID) References worker(worker_ID) on delete cascade
);
alter table Logistican
add Constraint lg_cord_id
Foreign key (Coordinator_Office_ID, Worker_Id) References Logistican(Office_ID, Worker_Id);
The relationship needs all elements of the primary key to be valid. I'm not sure if it needs to be a separate statement in Oracle.
I'm receiving this error when trying to create a table and I don't know why:
[2016-07-05 14:08:02] [42000][2270] ORA-02270: no matching unique or primary key for this column-list
This question seems different (to me) from a similar question, because in that question the OP is referencing a table with a composite PK, while I am not.
And while this other question has the same error code, it is because the OP is incorrectly references the primary key, which I don't think I did.
May someone more experienced in SQL educate me?
(A couple of things to note: 1) I know the table/column names have small errors/deviations from convention, but this is for homework, and the teacher requires I have the tables and rows declared exactly his way, even if it's non-conventional. 2) Yes, that's silly; but no, I can't change it or I get marked down.)
CREATE TABLE Student_Course
(
Stu_ID NUMBER(5) NOT NULL,
Course_ID VARCHAR2(8) NOT NULL,
Section# NUMBER(3),
CONSTRAINT pk_stu_crse PRIMARY KEY (Stu_ID, Course_ID),
CONSTRAINT fk_course_id FOREIGN KEY (Course_ID) REFERENCES course(Course_ID),
CONSTRAINT fk_stu_id FOREIGN KEY (Stu_ID) REFERENCES student(Stu_ID),
CONSTRAINT fk_section FOREIGN KEY (Section#) REFERENCES course(Section#)
)
There are only two, small, referenced tables, which are:
CREATE TABLE student
(
Stu_ID NUMBER(5) PRIMARY KEY ,
Lname VARCHAR2(20),
Fname VARCHAR2(20),
Mi CHAR(1),
Sex CHAR(1),
Major VARCHAR2(15),
Home_State CHAR(2)
);
CREATE TABLE course
(
Course_ID VARCHAR2(8) PRIMARY KEY ,
Section# NUMBER(3),
C_Name VARCHAR2(30),
C_Description VARCHAR2(30)
);
A foreign key is a reference to a primary key in another table.
The last constraint CONSTRAINT fk_section FOREIGN KEY (Section#) REFERENCES course(Section#) won't work - Section# isn't a primary key in that table
Section# Must be at least UNIQUE in course table.
If you want to use Section# as a reference for a foreign key, it must be a UNIQUE or a PRIMARY KEY
More information about FOREIGN KEY and constraints
Thanks to good answers, I'm posting my code which I corrected based on help here. Hope my corrections help others in the future.
CREATE TABLE student
(
Stu_ID NUMBER(5) PRIMARY KEY ,
Lname VARCHAR2(20),
Fname VARCHAR2(20),
Mi CHAR(1),
Sex CHAR(1),
Major VARCHAR2(15),
Home_State CHAR(2)
);
CREATE TABLE course
(
Course_ID VARCHAR2(8) ,
Section# NUMBER(3) ,
C_Name VARCHAR2(30),
C_Description VARCHAR2(30),
CONSTRAINT pk_course PRIMARY KEY (Course_ID, Section#)
);
CREATE TABLE Student_Course
(
Stu_ID NUMBER(5) ,
Course_ID VARCHAR2(8) ,
Section# NUMBER(3) ,
CONSTRAINT pk_stu_crse PRIMARY KEY (Stu_ID, Course_ID, Section#),
CONSTRAINT fk_stu FOREIGN KEY (Stu_ID) REFERENCES student(Stu_ID),
CONSTRAINT fk_course_id FOREIGN KEY (Course_ID, Section#) REFERENCES course(Course_ID, Section#)
);