mysql primary ferign key

mysql add foreign key

-- On Create
CREATE TABLE tableName (
    ID INT,
    SomeEntityID INT,
    PRIMARY KEY (ID),
    FOREIGN KEY (SomeEntityID)
        REFERENCES SomeEntityTable(ID)
        ON DELETE CASCADE
);

-- On Alter, if the column already exists but has no FK
ALTER TABLE
  tableName
ADD
  FOREIGN KEY (SomeEntityID) REFERENCES SomeEntityTable(ID) ON DELETE CASCADE;
  
 -- Add FK with a specific name
 -- On Alter, if the column already exists but has no FK
ALTER TABLE
  tableName
ADD CONSTRAINT fk_name
  FOREIGN KEY (SomeEntityID) REFERENCES SomeEntityTable(ID) ON DELETE CASCADE;

Posted by: Guest on April-27-2020

ALTER TABLE tableName MODIFY COLUMN id INT; /* First you should drop auto increment */ ALTER TABLE tableName DROP PRIMARY KEY; /* Dop primary key */ ALTER TABLE tableName ADD PRIMARY KEY (new_id); /* Set primary key to the new column */ ALTER TABLE tableName MODIFY COLUMN new_id INT AUTO_INCREMENT; /* Set auto increment to the new primary key */

Code answers related to "mysql primary ferign key"

Browse Popular Code Answers by Language

Answers for "mysql primary ferign key"

Code answers related to "mysql primary ferign key"

Code answers related to "SQL"

Browse Popular Code Answers by Language

Popular Programming Languages

Advertisements

Company

Compilers

Help

Connect with us