如何在PL / SQL的表格中插入“±，≧，≦”等字符

Question

这是我用来创建表格的SQL：

create table LAB_REQUESTS_REQUREMENTS
(
  id                 INTEGER not null,
  request_id         INTEGER not null,
  test_id            INTEGER not null,
  requrement         VARCHAR2(30) not null,
  assistant_id       INTEGER,
  measured_result    VARCHAR2(50),
  measured_condition VARCHAR2(50),
  price_id           INTEGER not null,
  single_price       NUMBER(15,2) default 0 not null,
  measured_date      DATE,
  measure            NVARCHAR2(30),
  metric_tolerance   NVARCHAR2(30)
)
tablespace VIK
  pctfree 10
  initrans 1
  maxtrans 255
  storage
  (
    initial 64K
    next 1M
    minextents 1
    maxextents unlimited
  );

我应该如何在'MEASURE'中插入这些字符，例如在插入然后从表中读取时不进行转换？