sql make sure every user is unqiuew
create table user(
user_id INT auto_increment PRIMARY KEY,
username varchar(50) not null,
avator varchar(50),
gender boolean not null,
phone varchar(20),
unique(username)
);
create table journey(
id INT auto_increment PRIMARY KEY,
start varchar(100) not null,
dest varchar(100) not null,
time date not null,
person INT,
user_id INT not null,
foreign key(user_id) references user(user_id)
);unique key
CREATE TABLE students
(
S_Id int NOT NULL,
LastName varchar (255) NOT NULL,
FirstName varchar (255),
City varchar (255),
UNIQUE (S_Id)
)unique key
Unique Key:
Only unique value and also can contain NULLCopyright © 2021 Codeinu
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