1.SQL的分类

  1.1DDL：数据定义语言

  1.2DML：数据操作语言

  1.3DQL：数据查询语言

  1.4DCL：数据控制语言

2.数据类型

  2.1字符型：char(不可变长)， varchar（可变长）

  2.2数字型：number(n,m) n代表总位数，m代表保留小数位数；float

  2.3日期型：date，timestamp

  2.4其他型：blob，clob，bfile

3.建表实例

--创建商品表CREATE TABLE goods(goods_id  varchar(255) primary key,goods_name  varchar(255),goods_type_id  varchar(255),goods_price  number(20,2),goods_stock  number,goods_agency  number);--创建商品类型表CREATE TABLE goods_type(goods_type_id  varchar(255) primary key,goods_type_name  varchar(255));--创建用户表CREATE TABLE customer(customer_id  varchar(255) primary key,customer_name  varchar(255),customer_pwd varchar(255),customer_mail varchar(255) check(customer_mail like '%@%'),customer_phone varchar(255),customer_create_date date NOT NULL);--创建订单表CREATE TABLE orderinfo(orderinfo_id varchar(255) primary key,orderinfo_customer varchar(255),orderinfo_addr varchar(255),orderinfo_pay_state int,constraint f_k foreign key(orderinfo_customer) references customer(customer_id) );--创建订单商品信息表CREATE TABLE order_goods_info(order_goods_info_id  varchar(255),order_goods_info_goods  varchar(255),order_goods_info_goodsnum  int,order_goods_info_orderid varchar(255),order_goods_info_customer  varchar(255),constraint f_k1 foreign key(order_goods_info_goods) references goods(goods_id),constraint f_k2 foreign key(order_goods_info_orderid) references orderinfo(orderinfo_id),constraint f_k3 foreign key(order_goods_info_customer) references customer(customer_id));

 4.表操作实例

--删除管道，杆路审核表DROP TABLE PIP_PIPELINE_CHECK;DROP TABLE PIP_POLELINE_CHECK;SELECT * FROM PIP_PIPELINE_CHECK;SELECT * FROM PIP_POLELINE_CHECK;--删除主键约束select * from user_cons_columns where table_name='PIP_PIPELINE_CHECK';alter table PIP_PIPELINE_CHECK drop constraint SYS_C00167278;--增加aa  字段ALTER TABLE PIP_PIPELINE_CHECK ADD AA VARCHAR(255);