刪除外鍵約束

表A的B_ID與表B的ID存在外鍵約束，創建語句如下：

ALTER TABLE A ADD ( FOREIGN KEY (B_ID) REFERENCES B);

 現在要刪除該外鍵約束：

declare
         v_constraint_name varchar2(30);

begin
        select constraint_name into v_constraint_name from user_constraints t Where t.table_name=upper('A') And t.constraint_type='R' And t.r_constraint_name In (Select constraint_name from user_constraints t Where t.table_name=upper('B') and t.constraint_type='P');

         execute immediate'Alter Table eis_elem_field Drop Constraint '||v_constraint_name;

commit; 
end;
/