SQL error - Failed to add the foreign key constraint - mysql

CREATE TABLE employee (
emp_id INT,
first_name VARCHAR(40),
last_name VARCHAR(40),
birth_day DATE,
sex VARCHAR(1),
salary INT,
super_id INT,
branch_id INT,
PRIMARY KEY (emp_id)
);
CREATE TABLE branch(
branch_id INT,
branch_name VARCHAR(40),
mgr_id INT,
mgr_start_date DATE,
FOREIGN KEY(mgr_id) REFERENCES employee(emp_id) ON DELETE SET NULL
);
ALTER TABLE employee
ADD FOREIGN KEY(branch_id)
REFERENCES branch(branch_id)
ON DELETE SET NULL;
I'm not sure what I'm doing wrong. When I run the lasts query, I keep getting the
"failed to add the foreign key constraint"
error saying there's a missing index for constraint 'employee_ibfk_2' in the reference table 'branch'


Columns referenced in a foreign key must be a key.
Presumably you forgot to declare branch_id as primary key?
Try:
...
CREATE TABLE branch(
branch_id INT,
branch_name VARCHAR(40),
mgr_id INT,
mgr_start_date DATE,
PRIMARY KEY (branch_id),
FOREIGN KEY(mgr_id) REFERENCES employee(emp_id) ON DELETE SET NULL
);
...


The branch_id column in your branch table is not indexed. a requirement for foreign key constraints.
Add an index like this:
ALTER TABLE `branch`
ADD INDEX `branch_id` (`branch_id` ASC) VISIBLE;
;

Related

Dropping a constraint with foreign key on POPSQL

I have tried to drop the employee table that I created but was unable to due to the constraints of the foreign key. when I drop the employee I get this error (Cannot drop table 'employee' referenced by a foreign key constraint 'branch_ibfk_1' on table 'branch')
CREATE TABLE employee (
emp_id INT PRIMARY KEY,
first_name VARCHAR(40),
last_name VARCHAR(40),
birth_day DATE,
sex VARCHAR(1),
salary INT,
super_id INT,
branch_id INT
);
ALTER TABLE employee
ADD FOREIGN KEY(branch_id)
REFERENCES branch(branch_id)
ON DELETE SET NULL;
ALTER TABLE employee
ADD FOREIGN KEY(super_id)
REFERENCES employee(emp_id)
ON DELETE SET NULL;
CREATE TABLE branch (
branch_id INT PRIMARY KEY,
branch_name VARCHAR(40),
mgr_id INT,
mgr_start_date DATE,
FOREIGN KEY(mgr_id) REFERENCES employee(emp_id) ON DELETE SET NULL
);

Do this :
Drop table branch;
Drop table employee;

Constraint does not exist unable to drop the table

CREATE TABLE employee (
emp_id INT PRIMARY KEY,
first_name VARCHAR(40),
last_name VARCHAR(40),
birth_day DATE,
sex VARCHAR(1),
salary INT,
super_id INT,
branch_id INT
);
CREATE TABLE branch (
branch_id INT PRIMARY KEY,
branch_name VARCHAR(40),
mgr_id INT,
mgr_start_date DATE,
FOREIGN KEY(mgr_id) REFERENCES employee(emp_id) ON DELETE SET NULL
);
ALTER TABLE employee
ADD FOREIGN KEY(branch_id)
REFERENCES branch(branch_id)
ON DELETE SET NULL;
ALTER TABLE employee
ADD FOREIGN KEY(super_id)
REFERENCES employee(emp_id)
ON DELETE SET NULL;
ALTER TABLE employee DROP CONSTRAINT branch_id;
Trying to Drop Constraint branch_id error says 'Constraint 'branch_id' does not exist.'
All I want to do is drop the employee table.

First find the name of the constraint with
SHOW CREATE TABLE employee
The name isn't "branch_id".

The actual name of your foreign key constraint is not branch_id, it is something else. The better approach here would be to name the constraint explicitly:
ALTER TABLE employee
ADD CONSTRAINT fk_branch_id FOREIGN KEY (branch_id)
REFERENCES branch(branch_id);
Then, delete it using the explicit constraint name you used above:
ALTER TABLE employee DROP FOREIGN KEY fk_branch_id;

I had a problem with my sql program with foreign keys

create database MALL;
use MALL;
create table customer (
customer_id int not null,
name varchar (20),
lastname varchar(20),
registration_date date,
primary key (customer_id)
);
create table inventory (
item_id int not null,
item_name varchar(20),
cost int,
primary key (item_id)
);
create table purchase (
purchase_date date,
purchase_count int,
customer_id int,
item_name varchar(20),
foreign key (customer_id) references customer(customer_id),
foreign key (item_name) references inventory(item_name)
);
I get this error
ERROR 1822 (HY000): Failed to add the foreign key constraint. Missing
index for constraint 'purchase_ibfk_2' in the referenced table
'inventory'

Here:
create table purchase (
...
foreign key (item_name) references inventory(item_name)
)
The column referenced by the foreign key needs a unique index: inventory(item_name) does not have that. I would simply recommend referencing the primary key of inventory rather than some other column:
create table purchase (
purchase_date date,
purchase_count int,
customer_id int,
item_id int,
foreign key (customer_id) references customer(customer_id),
foreign key (item_id) references inventory(item_id)
);

ER_FK_NO_INDEX_PARENT: Failed to add the foreign key constraint. Missing index for constraint 'employee_ibfk_10' in the referenced table 'branch'

I try to create a table for the company database.
As I tried to add some foreign keys in there, something goes wrong.
CREATE TABLE employee (
emp_id INT PRIMARY KEY,
first_name VARCHAR(40),
last_name VARCHAR(40),
birth_day DATE,
sex VARCHAR(1),
salary INT,
super_id INT,
branch_id INT unique
);
CREATE TABLE branch (
branch_id INT PRIMARY KEY,
branch_name VARCHAR(40),
mgr_id INT,
mgr_start_date DATE,
FOREIGN KEY(mgr_id) REFERENCES employee(emp_id) ON DELETE SET NULL
);
ALTER TABLE employee
ADD FOREIGN KEY(branch_id)
REFERENCES branch(branch_id)
ON DELETE SET NULL;
ALTER TABLE employee
ADD FOREIGN KEY(super_id)
REFERENCES employee(emp_id)
ON DELETE SET NULL
The "alter table employee" part to add foreign key (branch) failed with the following statement.
ER_FK_NO_INDEX_PARENT: Failed to add the foreign key constraint. Missing index for constraint 'employee_ibfk_10' in the referenced table 'branch'
Could this be some problem with my setting?

error in SQL syntax create table

I was trying to feed the following commands to MySQL CLI with
, which seems to be good, however when I added one more table, it complained there was an error in syntax.
Here are the commands
CREATE TABLE IF NOT EXISTS User(
uid INT,
name VARCHAR(64) UNIQUE,
birthday date,
PRIMARY KEY(uid)
) ENGINE = InnoDB ;
CREATE TABLE IF NOT EXISTS UserEmail(
uid INT,
email VARCHAR(64),
PRIMARY KEY(uid, email),
FOREIGN KEY(uid) REFERENCES User(uid)
);
However if I wanted to add one more table, it said there's an syntax error near the ')' at the line where PRIMARY KEY(uid) lies.
CREATE TABLE IF NOT EXISTS User(
uid INT,
name VARCHAR(64) UNIQUE,
birthday date,
PRIMARY KEY(uid)
) ENGINE = InnoDB ;
CREATE TABLE IF NOT EXISTS UserEmail(
uid INT,
email VARCHAR(64),
PRIMARY KEY(uid, email),
FOREIGN KEY(uid) REFERENCES User(uid)
);
CREATE TABLE friendship(
invite_uid INT,
accept_uid INT,
start_date DATE,
PRIMARY KEY(invite_uid, accept_uid),
FOREIGN KEY(invite_uid) REFERENCES User(uid),
FOREIGN KEY(accept_uid) REFERENCES User(uid),
);
Not sure where went wrong since the error was not complained in the newly added command.
--UPDATE--
Well that was fixed, but there's one more problem.
Adding the following table throws
cannot create table "estore.contains" (errorno: 150)
CREATE TABLE contains(
uid INT,
wid INT,
pid INT,
PRIMARY KEY(uid, wid, pid),
FOREIGN KEY(uid) REFERENCES User(uid),
FOREIGN KEY(wid) REFERENCES Wishlist(wid),
FOREIGN KEY(pid) REFERENCES Product(pid)
);
--UPDATE 2--
Full Tables that I want to add
CREATE TABLE IF NOT EXISTS User(
uid INT,
name VARCHAR(64) UNIQUE,
birthday date,
PRIMARY KEY(uid)
) ENGINE = InnoDB ;
CREATE TABLE IF NOT EXISTS UserEmail(
uid INT,
email VARCHAR(64),
PRIMARY KEY(uid, email),
FOREIGN KEY(uid) REFERENCES User(uid)
);
CREATE TABLE friendship(
invite_uid INT,
accept_uid INT,
start_date DATE,
PRIMARY KEY(invite_uid, accept_uid),
FOREIGN KEY(invite_uid) REFERENCES User(uid),
FOREIGN KEY(accept_uid) REFERENCES User(uid)
);
CREATE TABLE Seller(
sid INT,
name VARCHAR(64),
PRIMARY KEY(sid)
);
CREATE TABLE Product(
pid INT,
sid INT,
name VARCHAR(64),
description TEXT,
price DOUBLE,
PRIMARY KEY(pid),
FOREIGN KEY(sid) REFERENCES Seller(sid)
);
CREATE TABLE buy(
uid INT,
pid INT,
time DATE,
PRIMARY KEY(uid, pid),
FOREIGN KEY(uid) REFERENCES User(uid),
FOREIGN KEY(pid) REFERENCES Product(pid)
);
CREATE TABLE Wishlist(
uid INT,
wid INT,
start_time DATE,
end_time DATE,
PRIMARY KEY(uid,wid),
FOREIGN KEY(uid) REFERENCES User(uid)
);
CREATE TABLE conntains(
uid INT,
wid INT,
pid INT,
PRIMARY KEY(uid, wid, pid),
FOREIGN KEY(uid) REFERENCES User(uid),
FOREIGN KEY(wid) REFERENCES Wishlist(wid),
FOREIGN KEY(pid) REFERENCES Product(pid)
)ENGINE = InnoDB;
Anyone could help? Thx

Check the last line of your code
FOREIGN KEY(accept_uid) REFERENCES User(uid),
Remove the comma at the end.

remove , a end of line
FOREIGN KEY(accept_uid) REFERENCES User(uid),
--------------------------------------------^

There is an extra comma on the third table.
CREATE TABLE IF NOT EXISTS User(
uid INT,
name VARCHAR(64) UNIQUE,
birthday date,
PRIMARY KEY(uid)
) ENGINE = InnoDB ;
CREATE TABLE IF NOT EXISTS UserEmail(
uid INT,
email VARCHAR(64),
PRIMARY KEY(uid, email),
FOREIGN KEY(uid) REFERENCES User(uid)
);
CREATE TABLE friendship(
invite_uid INT,
accept_uid INT,
start_date DATE,
PRIMARY KEY(invite_uid, accept_uid),
FOREIGN KEY(invite_uid) REFERENCES User(uid),
FOREIGN KEY(accept_uid) REFERENCES User(uid), <---- Extra comma
);

FOREIGN KEY(accept_uid) REFERENCES User(uid),<-- Comma should be removed
Try this:
CREATE TABLE friendship(
invite_uid INT,
accept_uid INT,
start_date DATE,
PRIMARY KEY(invite_uid, accept_uid),
FOREIGN KEY(invite_uid) REFERENCES User(uid),
FOREIGN KEY(accept_uid) REFERENCES User(uid)
);

#Daniel, you cannot use the name CONTAINS for a table since its an SQL keyword. Please create the table with some other name.

Fortunately I figured the second problem out, the foreign key was not made right, I need to use
FOREIGN KEY(uid, wid) REFERENCES Wishlist(uid, wid),
to refer the the primary key combination in Wishlist