alter table add foreign key mysql
ALTER TABLE orders
ADD
FOREIGN KEY (user_id) REFERENCES users(id) ON DELETE CASCADE;alter table add foreign key mysql
ALTER TABLE orders
ADD
FOREIGN KEY (user_id) REFERENCES users(id) ON DELETE CASCADE;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;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)
);mysql foreign key constraints
ALTER TABLE Orders ADD CONSTRAINT FK_PersonOrder FOREIGN KEY (PersonID) REFERENCES Persons(PersonID);Copyright © 2021 Codeinu
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