I have all the primary keys and drop tables in the correct order.
I basically want stockID to be a foreign key in my refund table.
My schema looks like this...
CREATE TABLE refunds (
refundID SMALLINT AUTO_INCREMENT,
stockID SMALLINT,
refundDate DATE,
FOREIGN KEY (stockID) REFERENCES tblStock(stockID),
PRIMARY KEY (refundID)
);
CREATE TABLE tblStock (
stockID SMALLINT AUTO_INCREMENT,
stockName VARCHAR(60),
StockNumbers SMALLINT
);
When referencing another table for a foreign key reference, that table needs to already exist. And, the column being referenced should be a primary key. Try this:
CREATE TABLE tblStock (
stockID SMALLINT AUTO_INCREMENT PRIMARY KEY,
stockName VARCHAR(60),
StockNumbers SMALLINT
);
CREATE TABLE refunds (
refundID SMALLINT AUTO_INCREMENT,
stockID SMALLINT,
refundDate DATE,
FOREIGN KEY (stockID) REFERENCES tblStock(stockID),
PRIMARY KEY (refundID)
);
FOREIGN KEY (stockID) REFERENCES tblStock(stockID)
Is referencing a table that doesn't yet exist. Create tblStock first.
You are referencing a table that doesn't exist. Create it first.
In addition, you will want to index the key you are referencing. Make sure any value being referenced in your foreign key actually exists.
Related
Hello I have an issue when trying inserting multiple foreign keys to a table. I have searched a lot of hours and still I don't figure it out.. It pops this error. I don't know what else I can do about that. Also I tried to add constraint .. foreign key ... references command and it didn't work.
DROP DATABASE IF EXISTS db;
CREATE DATABASE db;
USE db;
CREATE TABLE BOOKS(
Bno int not null primary key auto_increment,
Title text,
PDate date,
Cno int,
Cname text
);
CREATE TABLE AUTHORS(
Ano int not null primary key auto_increment,
Asurname text,
Aname text
);
CREATE TABLE CATEGORIES(
Cno int not null primary key auto_increment,
Cname text,
No_Of_Books int
);
CREATE TABLE SUMMARY_LANG(
Bno int not null primary key auto_increment,
Language text,
FOREIGN KEY (Bno) REFERENCES BOOKS(Bno)
);
CREATE TABLE WRITER(
Bno int,
Ano int,
Asurname text,
Aname text,
FOREIGN KEY (Bno) REFERENCES BOOKS(Bno),
FOREIGN KEY (Ano) REFERENCES AUTHORS(Ano),
FOREIGN KEY (Asurname) REFERENCES AUTHORS(Asurname),
FOREIGN KEY (Aname) REFERENCES AUTHORS(Aname)
);
INSERT INTO BOOKS(Title,PDate,Cname)
VALUES
('A first course in database systems','2014-01-01','DATABASE'),
('FUNDAMENTAL CONCEPTS OF PROGRAMMING SYSTEMS','1976-01-01','PROGRAMMING');
ALTER TABLE AUTHORS auto_increment = 100;
INSERT INTO AUTHORS(Asurname,Aname)
VALUES
('ULLMAN','JEFF'),
('WIDOM','JENNIFER');
ALTER TABLE CATEGORIES auto_increment = 10;
INSERT INTO CATEGORIES(Cname, No_Of_Books)
VALUES
('DATABASE',1),
('PROGRAMMING',1);
INSERT INTO SUMMARY_LANG(Language)
VALUES
('ENG'),
('GRE'),
('ENG'),
('FRA');
Your definition of SUMMARY_LANG is wrong
CREATE TABLE SUMMARY_LANG(
Bno int not null primary key auto_increment,
Language text,
FOREIGN KEY (Bno) REFERENCES BOOKS(Bno) <-- remove this reference
);
Remove the foreign key, because this is a Table that is used only as reference number to another table also called a helper table, because the text would be redundant in the referenced table.
But i can't see any column that references language.
So add a column to BOOKS, where you add the reference to SUMMARY_LANG and when you add new rows SUMMARY_LANG you won't get any errors anymore.
So the new tables can be like this
CREATE TABLE BOOKS (
Bno INT NOT NULL PRIMARY KEY AUTO_INCREMENT,
Title TEXT,
PDate DATE,
Cno INT,
Cname TEXT,
SNno int,
FOREIGN KEY (SNno)
REFERENCES SUMMARY_LANG (SNno)
);
CREATE TABLE SUMMARY_LANG(
SNno int not null primary key auto_increment,
Language text
);
I have three tables A, B and funding:
Table A has a primary key partner_id
Table B has a primary key branch_id
When I try to create table C with the following code:
CREATE TABLE Funding (
partner_id INT,
branch_id INT,
total_fund FLOAT,
PRIMARY KEY (partners_id, branch_id),
FOREIGN KEY (partners_id) REFERENCES A(partner_id) ON delete SET NULL,
FOREIGN KEY (branch_id) REFERENCES B(branch_id) ON delete SET NULL
);
I get error message:
1830: column partner_id cannot be NOT NULL: needed in a foreign key constraint.
How can I solve this problem?
Create a separted ID for PK:
SQL DEMO
CREATE TABLE A (
partner_id INT,
PRIMARY KEY (partner_id)
);
CREATE TABLE B (
branch_id INT,
PRIMARY KEY (branch_id)
);
CREATE TABLE Funding (
id INT PRIMARY KEY AUTO_INCREMENT,
partner_id INT,
branch_id INT,
total_fund FLOAT,
FOREIGN KEY (partner_id) REFERENCES A(partner_id) ON DELETE SET NULL,
FOREIGN KEY (branch_id) REFERENCES B(branch_id) ON DELETE SET NULL
);
You can also add:
ALTER TABLE `Funding` ADD UNIQUE `unique_index`(partner_id, branch_id);
But that can cause problem when multiple partners from same branch are deleted
In CREATE TABLE Funding just add NOT NULL statement to partner_id and branch_id.
CREATE TABLE Funding ( partner_id INT NOT NULL, branch_id INT NOT NULL,...
I've got a problem creating a database.
I'd like to update children table using it's foreign key referencing to mother table automatically.
It means that when data values are inserted into the mother table, the children table gets updated on the column that is the foreign key.
Here's the code i wrote:
drop database domowa_biblioteka;
create database domowa_biblioteka;
use domowa_biblioteka;
create table pozycje
(
lp_p mediumint NOT NULL auto_increment,
nazwisko_autora char(30),
tytul char(60),
ilosc_stron int(4),
cena_oryginalna int(4),
na_sprzedaz enum('NIE','TAK'),
sprzedana enum('NIE','TAK'),
nr_pokoju mediumint,
PRIMARY KEY (lp_p)
)
;
create table kod_miedzynarodowy
(
lp_km mediumint,
ISBN char(20),
FOREIGN KEY (lp_km) REFERENCES pozycje (lp_p)
ON UPDATE CASCADE
)
;
create table pokoje
(
nr_pokoju mediumint NOT NULL auto_increment,
opis char(30),
PRIMARY KEY (nr_pokoju)
)
;
alter table pozycje ADD FOREIGN KEY (nr_pokoju) REFERENCES pokoje (nr_pokoju);
The thing is that the values of columns remain NULL after inserting data to rows.
Thanks for help!
im trying to create a products table with a primary and foreign key with this.
...
here is the code that i have tried so far
CREATE TABLE products
(
prod_id int NOT NULL,
prod_name int NOT NULL,
price varchar(15)
5on_hand varchar(15),
supp_id varchar(20),
PRIMARY KEY (prod_id),
FOREIGN KEY (supp_id)
);
any help would be greatly appreciated
A foreign key is a reference to a field in another table. To specify a foreign key, you have to specify what field(s) it refers to. The database cannot guess this.
So, guessing that supp_id refers to the id in the Suppliers table, your foreign key clause should look like this:
FOREIGN KEY (supp_id) REFERENCES Supplier(id)
I would strongly encourage the following:
All tables have an primary key column that is an integer and auto-incremented.
Names should be character strings.
Prices should be decimals.
So, I'm thinking something like this is appropriate:
CREATE TABLE Products (
ProductId int NOT NULL auto_increment primary key,
Name varchar(255) NOT NULL,
Price decimal(19, 4),
OnHand integer, -- assuming this is quantity on-hand
SupplierId int,
FOREIGN KEY (SupplierId) REFERENCES Suppliers(SupplierId)
);
These are my tables. I have a problem with the last one (Inscription) it doesn't accept CodeProjet as a foreign key. The error says table (Projet) doesn't have a primary key called CodeProjet but it does! I have used every trick that I know and nothing. I altered the table to add constraint, etc. Still nothing. I always get the same error. Here are the tables:
create database Gestion_Stages_Employe
create table Employe
(
NumEmploye int primary key,
NomEmploye varchar(15),
PrenomEmploye varchar(15),
SexeEmploye varchar(10),
DNaissEmploye date,
FonctionEmploye varchar(20)
)
create table TypeProjet
(
TypeProjet varchar(20) primary key,
libelleProjet varchar(20),
DureeProjet date,
)
create table Projet
(
CodeProjet int,
TypeProjet varchar(20),
DateDebut Date,
DateFin Date,
Constraint Pk_CodeProj primary key (CodeProjet,TypeProjet),
Constraint FK_TypeProj foreign key (TypeProjet) references TypeProjet(TypeProjet),
)
create table Inscription
(
NumEmploye int foreign key references Employe(NumEmploye),
CodeProjet int foreign key references Projet(CodeProjet),
dateiscription Date,
primary key (NumEmploye,CodeProjet),
)
As was mentioned in the comment, the Primary Key on the Projet table is a "composite key" (multiple columns are required to enforce uniqueness).
As a result, for your foreign key to work, you need to either remove "TypeProjet" from the primary key of Project (assuming CodeProjet is sufficient to uniquely identify a Projet), or you need to add TypeProjet to the Inscription table and define your foreign key with both columns, for example:
create table Inscription (
NumEmploye int foreign key references Employe(NumEmploye),
CodeProjet int,
dateiscription Date,
TypeProjet varchar(20),
Constraint fk_Inscription_project Foreign key (CodeProjet,TypeProjet) references Projet(CodeProjet,TypeProjet),
primary key (NumEmploye,CodeProjet),
)