I want to make Emp_id as a foreign key for Employee table and Record table. Can this be done?
This is my code
CREATE TABLE Empolyee(
EID varchar(8) NOT NULL,
E_name varchar(30) NOT NULL,
NID varchar(30) NOT NULL,
sex varchar(40) NOT NULL,
history varchar(30) NOT NULL,
salary varchar(10) NOT NULL,
cid int NOT NULL,
FOREIGN KEY (cid) REFERENCES Employee_Contact_No(CID),
FOREIGN KEY (cid) REFERENCES Employee_email(Email_ID),
PRIMARY KEY (EID)
);
Receptionist table
CREATE TABLE Receptionist(
r_id varchar(8) NOT NULL,
Emp_ID varchar(8) NOT NULL,
PRIMARY KEY (r_id),
FOREIGN KEY (Emp_ID) REFERENCES Employee(EID),
FOREIGN KEY (Emp_ID) REFERENCES Record(EID)
);
And the receptionist's records
CREATE TABLE Record(
record_no varchar(8) NOT NULL,
EID VARCHAR(8) Not Null,
patient_id varchar(15) NOT NULL,
discription varchar(30) NOT NULL,
appointment varchar(40) NOT NULL,
PRIMARY KEY (record_no)
);
You can make a single field reference multiple tables, but I cannot think of a scenario where it would ever be a good idea; it would require both tables to have the same id value, and (at least imply) that those id values be meaningfully coordinated.
From the looks of your examples, it is probably more likely that you need tables like Employee_Contact_No and Employee_email to reference the Employee table.
Related
so pretty new to SQL I created 2 tables which I wanted to be related to one another but I'm getting an error "#1215 - Cannot add foreign key constraint" can someone point me to the right direction of this problem?
CREATE TABLE movie(
id INT(1) NOT NULL AUTO_INCREMENT,
nearname VARCHAR(25) NOT NULL,
release_date DATE NOT NULL,
lang VARCHAR(10) NOT NULL,
PRIMARY KEY(id),
CONSTRAINT same_movie FOREIGN KEY(id) REFERENCES movie_cast(movie_id)
);
CREATE TABLE movie_cast(
movie_id INT(1) NOT NULL AUTO_INCREMENT,
director_name VARCHAR(20) NOT NULL,
actor_name VARCHAR(20) NOT NULL,
actress_name VARCHAR(20) NOT NULL,
PRIMARY KEY(movie_id),
CONSTRAINT same_movie FOREIGN KEY(movie_id) REFERENCES movie(id)
);
You need to refer to the same column name as the primary key. In this case, it is called id:
CONSTRAINT same_movie FOREIGN KEY(movie_id) REFERENCES movie_cast(id)
Of course, your DDL doesn't define movie_cast. So, I am guessing the second table should be something like:
CREATE TABLE movie_cast (
id INT NOT NULL AUTO_INCREMENT,
movie_id int not null,
cast_name varchar(255)
PRIMARY KEY(id),
CONSTRAINT fk_movie_cast_movie FOREIGN KEY(movie_id) REFERENCES movie(movie_id)
);
Hi I am wondering why I getting an error
ERROR 1452 (23000): Cannot add or update a child row: a foreign key
constraint fails (exams.entries, CONSTRAINT entries_ibfk_2
FOREIGN KEY (student_id) REFERENCES students (student_id))
Any help would be appriatiated!
Here are the scripts that I think are relevant to the problem I'm having,
First I made this table entries and everything was fine
CREATE TABLE entries(
subject_id INT UNSIGNED NOT NULL,
subject_name VARCHAR(60) NOT NULL,
level_of_entry VARCHAR(60) NOT NULL,
exam_board VARCHAR(60) NOT NULL,
student_id INT UNSIGNED NOT NULL AUTO_INCREMENT,
date_of_exam DATETIME NOT NULL,
PRIMARY KEY (date_of_exam),
FOREIGN KEY (subject_id)
REFERENCES subjects(subject_id),
FOREIGN KEY (student_id)
REFERENCES students(student_id)
Then I tried to insert data and I got the error.
INSERT INTO entries (subject_id,subject_name, level_of_entry, exam_board,date_of_exam)
VALUE ('1','chemistry','as','ocr','2017-05-05 12:00:00'),
('2','biology','gcse','aqa','2017-05-05 12:00:01'),
('3','music','gcse','edexcel','2017-05-05 12:00:02'),
('4','english','a','ocr','2017-05-05 12:00:03'),
('5','physics','a','aqa','2017-05-05 12:00:04'),
('6','maths','gcse','aqa','2017-05-05 12:00:05'),
('7','computing','gcse','aqa','2017-05-05 12:00:06'),
('8','physical_education','gcse','aqa','2017-05-05 12:00:07'),
('9','design_and_technology','gcse','aqa','2017-05-05 12:00:08'),
('10','french','gcse','aqa','2017-05-05 12:00:09');
It suggest on other questions similar to this to make sure your parent table has the same values but it does and its making know sense to me.
Here is the parent script.
CREATE TABLE IF NOT EXISTS students(
student_id INT UNSIGNED NOT NULL AUTO_INCREMENT,
first_name VARCHAR(20) NOT NULL,
middle_name VARCHAR(20) NOT NULL,
last_name VARCHAR(40) NOT NULL,
email VARCHAR(60) NOT NULL,
password CHAR(40) NOT NULL,
reg_date DATETIME NOT NULL,
PRIMARY KEY (student_id) ,
UNIQUE (email));
Here is the other parent script but I'm having no problems with it.
CREATE TABLE IF NOT EXISTS subjects(
subject_id INT UNSIGNED NOT NULL AUTO_INCREMENT,
subject_name VARCHAR(60) NOT NULL,
level_of_entry VARCHAR(60) NOT NULL,
exam_board VARCHAR(60) NOT NULL,
PRIMARY KEY (subject_id) ,
UNIQUE (subject_id));
If anyone could help I would be extremely grateful!
There are two issues with your logic related to student_id.
You should not have AUTO_INCREMENT in foreign key table.
A table which has a foreign key can't auto-populate values (logically and technically). It has to refer to some value in its Primary table. In your case, it is students table.
So, change your table structure as below:
CREATE TABLE entries(
subject_id INT UNSIGNED NOT NULL,
subject_name VARCHAR(60) NOT NULL,
level_of_entry VARCHAR(60) NOT NULL,
exam_board VARCHAR(60) NOT NULL,
student_id INT UNSIGNED NOT NULL,
date_of_exam DATETIME NOT NULL,
PRIMARY KEY (date_of_exam),
FOREIGN KEY (subject_id)
REFERENCES subjects(subject_id),
FOREIGN KEY (student_id)
REFERENCES students(student_id)
You should specify a value in your INSERT query for entries table
You need to ensure you insert a value manually in your entries table for student_id column.
A side not as specified in comments that you defined subject_id as INT but you are trying to insert character values.
Change your insert query as below:
INSERT INTO entries (subject_id,subject_name, level_of_entry, exam_board,date_of_exam, student_id)
VALUE (1,'chemistry','as','ocr','2017-05-05 12:00:00', 100),
(2,'biology','gcse','aqa','2017-05-05 12:00:01', 101);
Note: I assumed 100 and 101 as your existing student ids from students table. You need to replace them with the correct ids from your table.
I am receiving an error when attempting to create some tables in mysql with the foreign key
CREATE TABLE session (
code CHAR(2) NOT NULL,
date DATE,
room VARCHAR(30) NULL,
CONSTRAINT session_pk PRIMARY KEY (date),
CONSTRAINT session_fk FOREIGN KEY (code)
REFERENCES module(code));
CREATE TABLE module (
code CHAR(2) NOT NULL,
name VARCHAR(30) NOT NULL,
cost DECIMAL(8,2) NOT NULL,
credits TINYINT NOT NULL,
course_code CHAR(3) NOT NULL,
CONSTRAINT module_pk PRIMARY KEY (code));
Here are the two tables I am trying to create, the syntax I've used matches w3 schools and both data types are the same so I cannot see how this is incorrect, any help would be appreciated thanks :)
You're trying to create a foreign key on table before creating the referencing table.
Interchanging the order of query will work :
CREATE TABLE module (
`code` CHAR(2) NOT NULL,
name VARCHAR(30) NOT NULL,
cost DECIMAL(8,2) NOT NULL,
credits TINYINT NOT NULL,
course_code CHAR(3) NOT NULL,
CONSTRAINT module_pk PRIMARY KEY (`code`));
CREATE TABLE `session` (
`code` CHAR(2) NOT NULL,
`date` DATE,
room VARCHAR(30) NULL,
CONSTRAINT session_pk PRIMARY KEY (`date`),
CONSTRAINT session_fk FOREIGN KEY (`code`)
REFERENCES module(`code`));
Try this
CREATE TABLE module (
code CHAR(2) NOT NULL,
name VARCHAR(30) NOT NULL,
cost DECIMAL(8,2) NOT NULL,
credits TINYINT NOT NULL,
course_code CHAR(3) NOT NULL,
CONSTRAINT module_pk PRIMARY KEY (code));
CREATE TABLE session (
code CHAR(2) NOT NULL,
date DATE,
room VARCHAR(30) NULL,
CONSTRAINT session_pk PRIMARY KEY (date),
CONSTRAINT session_fk FOREIGN KEY (code)
REFERENCES module(code));
When I try to source these tables into MySQL, and it created all the tables. Then I start to populate the tables, and it will not let me populate the last table Rental_Invoice. Any suggestions?
The error is
ERROR 1452 (23000): Cannot add or update a child row: a foreign key
constraint fails (SFRC_HIDDEN.Rental_Invoice, CONSTRAINT
Rental_Invoice_fk_Client_Contact FOREIGN KEY (Client_ID)
REFERENCES Client_Contact (Client_ID))
create table Client_Contact
(
Client_ID int Primary Key Auto_Increment,
Client_First_Name varchar(50) Not Null,
Client_Last_Name varchar(50) Not Null,
Client_Address varchar(50),
Client_City varchar(50) Not Null,
Client_State Char(2) Not Null,
Client_Zip_Code varchar(20) Not Null,
Client_Phone varchar(20),
Client_Email varchar(30)
);
create table Owner_Contact
( Owner_ID int Primary Key,
Owner_First_Name varchar(50) Not Null,
Owner_Last_Name varchar(50) Not Null,
Owner_Address varchar(50),
Owner_City varchar(50) Not Null,
Owner_State varchar(2) Not Null,
Owner_Zip_Code varchar(20) Not Null,
Owner_Phone varchar(20),
Owner_Email varchar(30)
);
create table Property_Info
(Property_ID varchar(20) Primary Key,
Owner_ID int Not Null,
Property_Type varchar(30) Not Null,
Pets set('Yes','No') Not Null,
Internet set('yes','No') Not Null,
constraint Property_Info_fk_Owner_Contact
foreign key (Owner_ID)
references Owner_Contact (Owner_ID));
create table Rental_Invoice
( Invoice_ID int Primary Key,
Property_ID varchar(10) Not Null,
Client_ID int Not Null,
Arrival_Date date Not Null,
Departure_Date date Not Null,
Deposit_Amount decimal(5,2) Not Null,
Pet_Deposit_Amount decimal(7,2),
Pet_Type enum('cat', 'dog', ''),
Cleaning_Fee decimal(5,2) Not Null,
Rental_Rate decimal(5,2) Not Null,
Method_Of_Payment varchar(20) Not Null,
constraint Rental_Invoice_fk_Client_Contact foreign key (Client_ID) references Client_Contact (Client_ID)
);
Initial problem
Just a random guess since I don't have MySQL installed anywhere at the moment. But Client_ID in the dependent table is a VARCHAR and it refers to an INTEGER column in the parent table.
After Edit
The foreign key constraint is caused by inserting a row into Rental_Invoice that does not have a corresponding row in Client_Contact. In other words, your data violates the Rental_Invoice_fk_Client_Contact foreign key constraint that requires that Rental_Invoice.Client_ID refers to an existing row in Client_Contact with a matching Client_ID.
I am having trouble with mapping things on separate tables of data. There will be tables for DEPARTMENT_LOCATIONS, DEPARTMENT, EMPLOYEE, and PROJECT.
So far all of the tables are created other that PROJECT, because I am receiving the error message for the title of my question.
Below is the information that I used to create the tables that were created without errors:
EMPLOYEE Table:
CREATE TABLE EMPLOYEE
(FNAME VARCHAR(25) NOT NULL,
MINIT CHAR(1),
LNAME VARCHAR(25) NOT NULL,
SSN NUMBER(10) NOT NULL,
BDATE DATE NOT NULL,
ADDRESS VARCHAR(30) NOT NULL,
SEX CHAR(1) NOT NULL,
SALARY DECIMAL(6,2) NOT NULL,
SUPERSSN NUMBER(10),
DNO NUMBER (1) NOT NULL,
PRIMARY KEY (SSN),
FOREIGN KEY (DNO) REFERENCES DEPT_LOCATIONS(DNUMBER));
DEPARTMENT_LOCATIONS Table:
CREATE TABLE DEPT_LOCATIONS
(DNUMBER NUMBER(1) NOT NULL,
DLOCATION VARCHAR(25) NOT NULL,
PRIMARY KEY (DNUMBER));
DEPARTMENT Table:
CREATE TABLE DEPARTMENT
(DNUMBER NUMBER(1) NOT NULL,
DNAME VARCHAR(25) NOT NULL,
MGRSTARTDATE DATE NOT NULL,
MGRSSN NUMBER(10) NOT NULL,
PRIMARY KEY (DNUMBER),
FOREIGN KEY (DNUMBER) REFERENCES DEPT_LOCATIONS(DNUMBER),
FOREIGN KEY (MGRSSN) REFERENCES EMPLOYEE(SSN));
Now when I enter the following information for the PROJECT Table, I receive the error message "ORA-02270: no matching unique or primary key for this column-list.)
CREATE TABLE PROJECT
(PNUMBER NUMBER(2,1) NOT NULL PRIMARY KEY,
PNAME VARCHAR(25) NOT NULL,
PLOCATION VARCHAR(25) NOT NULL,
DNUM NUMBER(1) NOT NULL,
FOREIGN KEY (PLOCATION) REFERENCES DEPT_LOCATIONS(DLOCATION),
FOREIGN KEY (DNUM) REFERENCES DEPT_LOCATIONS(DNUMBER));
Why is this error occurring and what do I need to do to correct it? Thank you.
You have to declare dlocation as unique, inorder to reference it in another table.
CREATE TABLE DEPT_LOCATIONS
(DNUMBER NUMBER(1) NOT NULL,
DLOCATION VARCHAR(25) UNIQUE,
PRIMARY KEY (DNUMBER));