Mega Code Archive
Use alter table to add foreign key with cascade delete
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SQL>
SQL> -- Use alter table to add foreign key with cascade 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) not null,
4 supplier_name varchar2(50) not null
5 );
Table created.
SQL>
SQL>
SQL> ALTER TABLE products
2 add CONSTRAINT fk_supplier
3 FOREIGN KEY (supplier_id)
4 REFERENCES supplier(supplier_id)
5 ON DELETE CASCADE;
Table altered.
SQL>
SQL>
SQL> desc products;
Name Null? Type
----------------------------------------------------------------------------------------------------- -------- --------------------------------------------------------------------
PRODUCT_ID NOT NULL NUMBER(10)
SUPPLIER_ID NOT NULL NUMBER(10)
SUPPLIER_NAME NOT NULL 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>
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