Oracle PL/SQL/Constraints/DELETE SET NULL

Create a foreign key "set null on delete" with more than one field

SQL>
SQL>
SQL>
SQL> -- Create a foreign key "set null on delete" with more than one field
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, supplier_name)
  6      );
Table created.
SQL>
SQL>
SQL>     CREATE TABLE products
  2      (      product_id      numeric(10)     not null,
  3             supplier_id     numeric(10),
  4             supplier_name   varchar2(50),
  5             CONSTRAINT fk_supplier_comp
  6               FOREIGN KEY (supplier_id, supplier_name)
  7              REFERENCES supplier(supplier_id, supplier_name)
  8              ON DELETE SET NULL
  9      );
Table created.
SQL>
SQL>
SQL>     desc products;
 Name                                                                                                  Null?    Type
 ----------------------------------------------------------------------------------------------------- -------- --------------------------------------------------------------------
 PRODUCT_ID                                                                                            NOT NULL NUMBER(10)
 SUPPLIER_ID                                                                                            NUMBER(10)
 SUPPLIER_NAME                                                                                          VARCHAR2(50)
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>

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>