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How primary key in one table connect to another table with the same primary key?
I am trying to make it like this, which those two primary key in the table of CustomerCreditCard is connect to the table of Customer and table of Credit card]
https://i.stack.imgur.com/lIBUE.png
--3
CREATE TABLE Customer
(
CustomerID INT IDENTITY PRIMARY KEY,
FirstName VARCHAR(50) NOT NULL,
LastName VARCHAR(50) NOT NULL,
);
--5
CREATE TABLE CreditCard
(
CreditCardNumber VARCHAR(16) PRIMARY KEY,
CreditCardOwnerName VARCHAR(50) NOT NULL,
);
--6
CREATE TABLE CustomerCreditCard
(
CreditCardNumber VARCHAR(16) NOT NULL,
CustomerID INT IDENTITY NOT NULL,
PRIMARY KEY(CreditCardNumber, CustomerID)
);
--6
CREATE TABLE CustomerCreditCard
(
CreditCardNumber VARCHAR(16) NOT NULL,
CustomerID INT NOT NULL,
CONSTRAINT pk_CustomerCreditCard
PRIMARY KEY(CreditCardNumber,CustomerID ),
CONSTRAINT fk_CustomerCreditCard_CreditCardNumber
FOREIGN KEY(CreditCardNumber)
REFERENCES CreditCard(CreditCardNumber)
ON DELETE CASCADE ON UPDATE CASCADE,
CONSTRAINT fk_CustomerCreditCard_CustomerID
FOREIGN KEY(CustomerID)
REFERENCES Customer(CustomerID)
ON DELETE CASCADE ON UPDATE CASCADE
);
To solve the problem of this question, add the foreign key to the table that has two primary keys, then reference to other tables that you want to connect with the same primary key.
I am trying to create SQL statements for an assignment in SQL Fiddle and I keep getting the error "Cannot add foreign key constraint". I have tried various things but I recieve different errors when I change things. What am I doing wrong?
CREATE TABLE Person (
ID int NOT NULL,
FName varchar(255),
LName varchar(255),
Preferred_Name varchar(255),
PRIMARY KEY (ID)
)
;
CREATE TABLE Song (
ID varchar(255) NOT NULL,
Title varchar(255),
Run_Time varchar(255),
Lyrics varchar(255),
LeadID int,
FOREIGN KEY (LeadID) REFERENCES Person(ID),
PRIMARY KEY (ID)
)
;
CREATE TABLE Album (
Title varchar(255) NOT NULL,
Run_Time int,
Release_Year TIMESTAMP,
PRIMARY KEY (Title)
)
;
CREATE TABLE Has (
Album_Title varchar(255),
Song_Title varchar(255),
FOREIGN KEY (Album_Title) REFERENCES Album(Title),
FOREIGN KEY (Song_Title) REFERENCES Song(ID)
)
;
CREATE TABLE Part_Of (
PersonID int,
SongID int,
Role varchar(255) NOT NULL,
FOREIGN KEY (PersonID) REFERENCES Person(ID),
FOREIGN KEY (SongID) REFERENCES Song(ID),
PRIMARY KEY (Role)
)
;
In the Song and Has tables you defined Song.ID and Has.Song_Title as a varchar(255). In the Part_Of table you defined SongID as an int. This is why the foreign key is failing. Use the same datatype in all tables (INT seems like a good option) to fix this.
CREATE TABLE Song (
ID varchar(255) NOT NULL, <------
Title varchar(255),
Run_Time varchar(255),
Lyrics varchar(255),
LeadID int,
FOREIGN KEY (LeadID) REFERENCES Person(ID),
PRIMARY KEY (ID)
)
;
CREATE TABLE Has (
Album_Title varchar(255),
Song_Title varchar(255), <-----
FOREIGN KEY (Album_Title) REFERENCES Album(Title),
FOREIGN KEY (Song_Title) REFERENCES Song(ID)
)
;
CREATE TABLE Part_Of (
PersonID int,
SongID int, <-----
Role varchar(255) NOT NULL,
FOREIGN KEY (PersonID) REFERENCES Person(ID),
FOREIGN KEY (SongID) REFERENCES Song(ID),
PRIMARY KEY (Role)
)
;
Would appreciate help. Can not create the "Teaches" and "takes" table.
CREATE DATABASE university;
use university;
CREATE TABLE classroom(
building VARCHAR(20),
room_number INT,
capacity INT,
PRIMARY KEY (building,room_number)
) ;
CREATE TABLE Sales(
item VARCHAR(20),
color VARCHAR(20),
clothes_size VARCHAR(20),
quantity INT,
PRIMARY KEY (item,color,clothes_size,quantity)
);
CREATE TABLE Department (
dept_name VARCHAR(20),
building VARCHAR(20),
budget INT,
FOREIGN KEY (building) references classroom(building),
PRIMARY KEY (dept_name,building,budget)
);
CREATE TABLE Course (
course_id VARCHAR(20)PRIMARY KEY,
title VARCHAR(20),
dept_name VARCHAR(20),
credits INT,
FOREIGN KEY (dept_name) references Department(dept_name)
);
CREATE TABLE Instructor(
ID VARCHAR(20) PRIMARY KEY,
neme VARCHAR(20),
dept_name VARCHAR(20),
salary INT,
FOREIGN KEY (dept_name) references Department(dept_name)
);
CREATE TABLE section(
course_id VARCHAR(20),
sec_id INT,
semester VARCHAR(20),
year1 INT,
building1 VARCHAR(20),
room_number INT,
time_slot_id CHAR,
FOREIGN KEY (course_id) REFERENCES Course(course_id),
FOREIGN KEY (building1,room_number) references classroom(building,room_number),
PRIMARY KEY(course_id,sec_id,semester,year1)
);
CREATE TABLE Teaches(
ID VARCHAR(20),
course_id VARCHAR(20),
sec_id VARCHAR(20),
semester VARCHAR(20),
year1 INT,
FOREIGN KEY (ID) references Instructor(ID),
FOREIGN KEY (sec_id) references section(sec_id),
FOREIGN KEY (semester,year1) references section(semester,year1),
FOREIGN KEY (course_id) references course(course_id),
PRIMARY KEY (ID,course_id,sec_id,year1,semester)
);
CREATE TABLE student(
ID VARCHAR(20) PRIMARY KEY,
name1 VARCHAR(20),
dept_name VARCHAR(20),
tot_cred INT);
CREATE TABLE Takes(
ID VARCHAR(20),
course_id VARCHAR(20),
sec_id INT,
semester VARCHAR(20),
year1 INT,
grade char,
FOREIGN KEY (ID) references student(ID),
FOREIGN KEY (sec_id) references section(sec_id),
FOREIGN KEY (semester) references section(semester),
FOREIGN KEY (year1) references section(year1),
FOREIGN KEY (course_id) references course(course_id),
PRIMARY KEY(ID,sec_id,semester,year1,course_id)
);
Foreign key references need to have the same types as the primary keys they refer to. So consider:
CREATE TABLE Department (
dept_name VARCHAR(20),
building VARCHAR(20),
budget INT,
FOREIGN KEY (building) references classroom(building),
PRIMARY KEY (dept_name,building,budget)
);
CREATE TABLE Instructor (
ID VARCHAR(20) PRIMARY KEY,
neme VARCHAR(20),
dept_name VARCHAR(20),
salary INT,
FOREIGN KEY (dept_name) references Department(dept_name)
);
The primary key for Department has three components -- dept_name, building, budget. However, the reference has only one component. They cannot match; the number is not correct, much less the types.
I would recommend that you use auto-incremented ids for your primary keys. You can also specify uniqueness constraints, if you like. So for this small example:
create table buildings (
building_id int auto_increment primary key,
building varchar(20),
constraint unq_buildings_building unique(building)
);
create table classrooms (
classroom_id int auto_increment primary key,
building_id int,
room_number int,
capacity int,
constraint fk_classrooms_building_id foreign key (building_id) references buildings (building_id)
) ;
create table Departments (
department_id int auto_increment primary key,
dept_name varchar(20),
building_id int,
budget INT,
constraint fk_departments_building_id foreign key (building_id) references buildings(building_id)
);
create table instructors (
instructor_id int auto_increment primary key,
id varchar(20) unique,
name varchar(20),
department_id int,
salary int,
foreign key instructors_department_id foreign key (department_id) references departments (department_id)
);
This is just a small sample of your tables. But the following are some rules that I follow:
Table names are plural.
They have a primary key which is the singular form followed by _id (or Id).
Foreign key references are only to primary keys.
To the extent possible, foreign keys and primary keys have the exact same name.
Explicit constraints are given names. The names follow a very precise naming convention.
I also added a buildings table. It is referenced in at least two places, so it seems worthy of being its own entity.
This should give you some ideas on how to build your database.
I am getting an error when i create my tabels.
The problem is that AssCode is not unique, so i can set it to unique, the combination of courseCode and AssCode is unique, thats why they are set as primary keys. I am using postgressql
here is the error:
ERROR: there is no unique constraint matching given keys for referenced table "assignments"
SQL state: 42830
here is my code:
CREATE TABLE Teachers (
BSN int primary key,
Surname varchar(40) NOT NULL,
Name varchar(40) NOT NULL
);
CREATE TABLE Courses (
CourseCode varchar(10) primary key,
Name varchar(20) NOT NULL
);
CREATE TABLE Assignments (
CourseCode varchar(10) REFERENCES Courses ON DELETE CASCADE,
AssCode varchar(10),
primary key(CourseCode,AssCode),
DependOn varchar(10),
Year date,
week int
);
CREATE TABLE WorkOn (
BSN int REFERENCES Teachers(BSN),
CourseCode varchar(10) REFERENCES Assignments(CourseCode),
AssCode varchar(10) REFERENCES Assignments(AssCode),
primary key (CourseCode,BSN,AssCode)
);
I found the answer:
CREATE TABLE WorkOn (
BSN int primary key REFERENCES Teachers(BSN),
CourseCode varchar(10),
AssCode varchar(10),
foreign key (CourseCode, AssCode) references Assignments (CourseCode, AssCode)
);
I have Assignment due in which i'm stuck on a question.
Add a “Sales Detail” table to your database. This table is related to the Orders and Products tables. It shows the product and quantity ordered at least (add other fields if you wish but explain why you added them on your paper).
There is no description of this table on the diagram provided. Use your best database design skills here!
Create Table SalesDetail
(
SaleDetailID int,
ProductID char(5),
ManufactureID char(3) not null,
OrderNo int,
qtyOrdered int
PRIMARY
)
Alter Table SalesDetail
Add FOREIGN KEY (ProductID)
REFERENCES Products(ProductID)
My Error is I can not get it to link SalesDetail table to Products table.
Msg 1776, Level 16, State 0, Line 1
There are no primary or candidate keys in the referenced table 'Products' that match the referencing column list in the foreign key 'FK__SalesDeta__Produ__5EBF139D'.
Msg 1750, Level 16, State 0, Line 1
Could not create constraint. See previous errors.
Create Table Customers
(
CustomerNo char(4)
Constraint ck_CustomerNoHas4positionsWithNumbers
Check(CustomerNo like'[0-9],[0-9],[0-9],[0-9]'),
Company varchar(50) not null,
CustomerRep char(3),
CreditLimt money default(20000.00),
PRIMARY KEY(CustomerNo)
)
Create Table Salesreps
(
EmployeeNo char(3)
Constraint ck_EmployeeNoHasDigits check(EmployeeNo like'[0-9],[0-9],[0-9]'),
FirstName varchar(25) not null,
LastName varchar(25) not null,
Age int,
SalesRepOffice char(2) not null,
Title varchar(50),
HireDate Date not null,
Manager char(3) not null,
Quota money,
Sales money not null,
PRIMARY KEY(EmployeeNo)
)
Create Table Offices
(
Office char(2) Constraint ck_checkOfficeHasNumbersOnly check(Office like'[0-9],[0-9]'),
City varchar(25) not null,
Region varchar(10) not null,
Manager char(3) not null,
Target money,
Sales money not null
PRIMARY KEY(Office)
)
Create Table Orders
(
OrderNo int,
OrderDate Date not null,
CustomerNo char(4) not null,
SalesRep char(3) not null
PRIMARY KEY(OrderNo)
)
Create Table Products
(
ManufactureID char(3)
Constraint ck_ManufactureIDifItHasLettersOnly check(ManufactureID like'[a-z],[a-z],[a-z]'),
ProductID char(5)
Constraint ck_ProductIDhasTwoLettersAndThreeNumbers check(ProductID like'[0-9],[0-9],[a-z],[a-z],[a-z]'),
Description varchar(50) not null,
Price money not null,
QtyOnHand int not null,
PRIMARY KEY(ManufactureID, ProductID)
)
--Add Foreign Keys to all tables who needs them
Alter Table Customers
Add constraint fk_customerrep
FOREIGN KEY (CustomerRep)
REFERENCES Salesreps(EmployeeNo)
Alter Table Salesreps
Add constraint fk_salesrepoffice
FOREIGN KEY (SalesRepOffice)
REFERENCES Offices(Office),
constraint fk_manager
FOREIGN KEY (Manager)
REFERENCES Salesreps(EmployeeNo)
Alter Table Offices
Add constraint fk_officesmanger
FOREIGN KEY (Manager)
REFERENCES Salesreps(EmployeeNo)
Alter Table Orders
Add constraint fk_customerno
FOREIGN KEY (CustomerNo)
REFERENCES Customers(CustomerNo),
constraint fk_salesrep
FOREIGN KEY (SalesRep)
REFERENCES Salesreps(EmployeeNo)
The table Products has a composite key (ManufactureID, ProductID), so you cannot uniquely identify a product by just the ProductId. Therefore you have to create a composite foreign key that references to both ManufactureId and ProductID:
Alter Table SalesDetail
Add FOREIGN KEY (ManufactureId, ProductID)
REFERENCES Products(ManufactureID, ProductID)
ProductID is not a primary key like the error says. In your code
PRIMARY KEY(ManufactureID, ProductID)
This creates a primary key that both of those columns combined.
The primary key for Products is (ManufactureID, ProductID). So the SalesDetail table should contain both these columns, and both should be part of the foreign key constraint:
Alter Table SalesDetail
Add FOREIGN KEY (ManufactureID, ProductID)
REFERENCES Products(ManufactureID, ProductID)