Answers for "mysql how to add foreign key to existing table"

SQL
6

alter table add foreign key mysql

ALTER TABLE orders
ADD 
FOREIGN KEY (user_id) REFERENCES users(id) ON DELETE CASCADE;
Posted by: Guest on May-29-2020
25

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
1

mysql alter add foreign key

ALTER TABLE ordenes ADD ticket VARCHAR(50) NOT NULL;
ALTER TABLE ordenes ADD CONSTRAINT fk_ticket FOREIGN KEY (ticket) REFERENCES tickets(ticket);
Posted by: Guest on October-19-2020
0

create table mysql with foreign key

CREATE TABLE Orders (
    OrderID int NOT NULL,
    OrderNumber int NOT NULL,
    PersonID int,
    PRIMARY KEY (OrderID),
    FOREIGN KEY (PersonID) REFERENCES Persons(PersonID)
);
Posted by: Guest on November-03-2020

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