sql 学习

create table `product_category` (
    `category_id` int not null auto_increment,
    `category_name` varchar(64) not null comment '类目名字',
    `category_type` int not null comment '类目编号',
    `create_time` timestamp not null default current_timestamp comment '创建时间',
    `update_time` timestamp not null default current_timestamp on update current_timestamp comment '修改时间',
    primary key (`category_id`)
);

create table `product_info` (
    `product_id` varchar(32) not null,
    `product_name` varchar(64) not null comment '商品名称',
    `product_price` decimal(8,2) not null comment '单价',
    `product_stock` int not null comment '库存',
    `product_description` varchar(64) comment '描述',
    `product_icon` varchar(512) comment '小图',
    `product_status` tinyint(3) DEFAULT '0' COMMENT '商品状态,0正常1下架',
    `category_type` int not null comment '类目编号',
    `create_time` timestamp not null default current_timestamp comment '创建时间',
    `update_time` timestamp not null default current_timestamp on update current_timestamp comment '修改时间',
    primary key (`product_id`)
);

create table `order_master` (
    `order_id` varchar(32) not null,
    `buyer_name` varchar(32) not null comment '买家名字',
    `buyer_phone` varchar(32) not null comment '买家电话',
    `buyer_address` varchar(128) not null comment '买家地址',
    `buyer_openid` varchar(64) not null comment '买家微信openid',
    `order_amount` decimal(8,2) not null comment '订单总金额',
    `order_status` tinyint(3) not null default '0' comment '订单状态, 默认为新下单',
    `pay_status` tinyint(3) not null default '0' comment '支付状态, 默认未支付',
    `create_time` timestamp not null default current_timestamp comment '创建时间',
    `update_time` timestamp not null default current_timestamp on update current_timestamp comment '修改时间',
    primary key (`order_id`),
    key `idx_buyer_openid` (`buyer_openid`)
);

create table `order_detail` (
    `detail_id` varchar(32) not null,
    `order_id` varchar(32) not null,
    `product_id` varchar(32) not null,
    `product_name` varchar(64) not null comment '商品名称',
    `product_price` decimal(8,2) not null comment '当前价格,单位分',
    `product_quantity` int not null comment '数量',
    `product_icon` varchar(512) comment '小图',
    `create_time` timestamp not null default current_timestamp comment '创建时间',
    `update_time` timestamp not null default current_timestamp on update current_timestamp comment '修改时间',
    primary key (`detail_id`),
    key `idx_order_id` (`order_id`)
);

create table `seller_info` (
    `id` varchar(32) not null,
    `username` varchar(32) not null,
    `password` varchar(32) not null,
    `openid` varchar(64) not null comment '微信openid',
    `create_time` timestamp not null default current_timestamp comment '创建时间',
    `update_time` timestamp not null default current_timestamp on update current_timestamp comment '修改时间',
    primary key (`id`)
) comment '卖家信息表';

-- 创建库
CREATE DATABASE mp;
-- 使用库
USE mp;
-- 创建表
CREATE TABLE tbl_employee(
   id INT(11) PRIMARY KEY AUTO_INCREMENT,
   last_name VARCHAR(50),
   email VARCHAR(50),
   gender CHAR(1),
   age INT
);
INSERT INTO tbl_employee(last_name,email,gender,age) VALUES('Tom','tom@atguigu.com',1,22);
INSERT INTO tbl_employee(last_name,email,gender,age) VALUES('Jerry','jerry@atguigu.com',0,25);
INSERT INTO tbl_employee(last_name,email,gender,age) VALUES('Black','black@atguigu.com',1,30);
INSERT INTO tbl_employee(last_name,email,gender,age) VALUES('White','white@atguigu.com',0,35);
SELECT  * FROM tbl_employee;
EXPLAIN DELETE FROM tbl_employee WHERE id = 100
CREATE TABLE  tbl_user(
  id INT(11) PRIMARY KEY  AUTO_INCREMENT,
  NAME VARCHAR(50),
  logic_flag INT(11)
)

-- Oracle
-- 创建一个测试表
drop table tbl_user;
create table tbl_user(
  id number(11) primary key,
  name varchar2(50),
  logic_flag number(11) 
);
-- 序列
create sequence seq_user start with 100 increment by 2 ;
-- 序列的常用操作
-- 查询序列的下一个值
select seq_user.nextval from dual;
-- 查询序列的当前值
select seq_user.currval from dual ;
select * from tbl_user;
```