On delete set null : Foreign Key « Key « SQL / MySQL

1. SQL / MySQL
2. Key
3. Foreign Key

On delete set null

      
mysql>
mysql> CREATE TABLE EmployeeS(
    ->          EmployeeNO       INTEGER      NOT NULL,
    ->          NAME           CHAR(15)     NOT NULL,
    ->          INITIALS       CHAR(3)      NOT NULL,
    ->          BIRTH_DATE     DATE                 ,
    ->          SEX            CHAR(1)      NOT NULL,
    ->          JOINED         SMALLINT     NOT NULL,
    ->          STREET         VARCHAR(30)  NOT NULL,
    ->          HOUSENO        CHAR(4)              ,
    ->          POSTCODE       CHAR(6)              ,
    ->          TOWN           VARCHAR(30)  NOT NULL,
    ->          PHONENO        CHAR(13)             ,
    ->          LEAGUENO       CHAR(4)              ,
    ->          PRIMARY KEY    (EmployeeNO)           );

mysql>
mysql>
mysql> CREATE   TABLE PENALTIES
    ->         (PAYMENTNO     INTEGER NOT NULL,
    ->          EmployeeNO      INTEGER NOT NULL,
    ->          PAYMENT_DATE  DATE NOT NULL,
    ->          AMOUNT        DECIMAL(7,2) NOT NULL,
    ->          PRIMARY KEY  (PAYMENTNO),
    ->          FOREIGN KEY  (EmployeeNO) REFERENCES EmployeeS (EmployeeNO)
    ->             ON DELETE SET NULL);

mysql>

   
    
    
    
    
    
  

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