如何在此SQL查询中修复无效的数据类型大小？

Question

我写为的查询

CREATE TABLE Shopper (
    Shopperid NUMBER(4) CONSTRAINT shpr_shprid_pk PRIMARY KEY,
    ShopperName VARCHAR2(20) CONSTRAINT shpr_shprname_nn NOT NULL,
    Gender CHAR(6) CONSTRAINT shpr_gdr_chk CHECK(Gender IN ('Male','Female')),
    MobileNo NUMBER(10) CONSTRAINT shpr_mobno_nn NOT NULL,
    Address VARCHAR2(50)
);