Sql foreign key

Alter table add column and foreign key mysql

ALTER TABLE database.table
  ADD COLUMN columnname INT DEFAULT(1),
  ADD FOREIGN KEY fk_name(fk_column) REFERENCES reftable(refcolumn) ON DELETE CASCADE;

Source: stackoverflow.com

Foreign key

USE Organization
CREATE TABLE Employee_Office
(
Id INT PRIMARY KEY IDENTITY(1,1),
Emp_Id int FOREIGN KEY REFERENCES Employee(Id),
Office_Id int FOREIGN KEY REFERENCES Office(Id)
)

Source: codingsight.com

Sql foreign key

create table Jobs(
job_id number not null,
job_title varchar(30),
min_salary number,
max_salary number
);
create table job_history(
employee_id number not null,
start_date date,
end_date date,
job_id number not null,
department_id number
);
alter table jobs add constraint pk_jobs primary key(job_id);
alter table job_history add constraint fk_job foreign key(job_id) references jobs(job_id);

Foreign key in sql dbms

FOREIGN KEY (fk_col_name) 
REFERENCES target_table_name (pk_col_name);

Source: launchschool.com

Foreign key

CREATE TABLE Employee(
    EmployeeID int NOT NULL,
    LastName varchar(50) NOT NULL,
    FirstName varchar(20) NOT NULL,
    Age int,
    DeptNo int,
    PRIMARY KEY (EmployeeID),
    FOREIGN KEY (DeptNo) REFERENCES Department(DeptNo)
);

Source: computerscienceai.com

Foreign key

USE Organization
CREATE TABLE Employee
(
Id INT PRIMARY KEY IDENTITY(1,1),
Name VARCHAR (50) NOT NULL,
Age INT,
Gender VARCHAR (50),
Dep_Id int FOREIGN KEY REFERENCES Department(Id),
Insur_Id int FOREIGN KEY REFERENCES Insurance(Id)
)

Source: codingsight.com

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