删除外键约束

表A的B_ID与表B的ID存在外键约束，创建语句如下：

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

 现在要删除该外键约束：

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;
/