Foreign Keys with 'set null on delete' : DELETE SET NULL « Constraints « Oracle PL / SQL

1. Oracle PL / SQL
2. Constraints
3. DELETE SET NULL

Foreign Keys with 'set null on delete'

SQL>
SQL> -- Foreign Keys with 'set null on delete'
SQL>
SQL>     CREATE TABLE supplier
  2      (      supplier_id     numeric(10)     not null,
  3             supplier_name   varchar2(50)    not null,
  4             contact_name    varchar2(50),
  5             CONSTRAINT supplier_pk PRIMARY KEY (supplier_id)
  6      );

Table created.

SQL>
SQL>
SQL>     CREATE TABLE products
  2      (      product_id      numeric(10)     not null,
  3             supplier_id     numeric(10),
  4             CONSTRAINT fk_supplier
  5               FOREIGN KEY (supplier_id)
  6              REFERENCES supplier(supplier_id)
  7              ON DELETE SET NULL
  8      );

Table created.

SQL>
SQL>     desc products;
 Name                                                                                                  Null?    Type
 ----------------------------------------------------------------------------------------------------- -------- --------------------------------------------------------------------

 PRODUCT_ID                                                                                            NOT NULL NUMBER(10)
 SUPPLIER_ID                                                                                            NUMBER(10)

SQL>     desc supplier;
 Name                                                                                                  Null?    Type
 ----------------------------------------------------------------------------------------------------- -------- --------------------------------------------------------------------

 SUPPLIER_ID                                                                                           NOT NULL NUMBER(10)
 SUPPLIER_NAME                                                                                         NOT NULL VARCHAR2(50)
 CONTACT_NAME                                                                                           VARCHAR2(50)

SQL>
SQL>     drop table products cascade constraints;

Table dropped.

SQL>
SQL>     drop table supplier cascade constraints;

Table dropped.

SQL>
SQL>
           
       

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