Answers for "mysql 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
3

fk in insert mysql

INSERT INTO joke(joke_text, joke_date, author_id)
VALUES (‘Humpty Dumpty had a great fall.’, ‘1899–03–13’, 
        (SELECT id FROM author WHERE author_name = ‘Famous Anthony’));
Posted by: Guest on November-17-2020
1

add column mysql with foreign key

ALTER TABLE `TABLE_NAME`
ADD COLUMN `COLUMN_NAME` BIGINT(20) UNSIGNED NULL DEFAULT NULL AFTER `AFTER_COLUMN_NAME`, 
ADD FOREIGN KEY `FOREIGN_RELATION_NAME`(`COLUMN_NAME`) REFERENCES `FOREIGN_TABLE`(`FOREIGN_COLUMN`)  ON UPDATE SET NULL ON DELETE SET NULL
Posted by: Guest on December-24-2020
2

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;
Posted by: Guest on June-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

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