Mysql初始

/*查询所有数据库*/
show databases;
/*创建数据库*/
CREATE TABLE dept(
    deptid INT,
    deptname VARCHAR(10),
    deptplace VARCHAR(50),
    createtime DATETIME
)
/*查看数据库*/
show create database emp;
/*删除数据库*/
drop database emp;
/*向已有的数据库中添加字段*/
ALTER TABLE dept ADD COLUMN compny VARCHAR(20);/*删除表中已有的字段*/
ALTER TABLE dept DROP COLUMN compny;
/*修改字段类型*/
ALTER TABLE bigpig MODIFY COLUMN createtime VARCHAR(20);
/*修改字段名称*/
ALTER TABLE dept CHANGE COLUMN deptplace age INT;

/*查看所有表语句*/
show tables;
/*创建表*/
CREATE TABLE table_name
(
    field1  datatype,
    field2  datatype,
    field3  datatype
)
/*创建表之前先使用use+数据库名称来使用制定数据库*/
/*删除表*/
drop table student;
/*修改表明称*/
ALTER TABLE dept RENAME TO bigpig;
/*查询表结构*/
DESC bigpig;
/*向表中添加数据*/
INSERT INTO bigpig VALUES(1,‘男‘,18,‘shshsh‘);
INSERT INTO person(NAME,age,money) VALUES(‘乔治‘,20,6000);
/*查询表中所有数据*/
SELECT * FROM bigpig;
UPDATE bigpig SET age=‘16‘ WHERE age=‘18‘;
/*删除数据*/
DELETE FROM bigpig WHERE age=‘18‘;
/*全表删除*/
DELETE FROM;
TRUNCATE TABLE;

-- 第一题
CREATE TABLE shangpin(
    pro_id INT,
    pro_name VARCHAR(30),
    protype_id INT,
    price DOUBLE,
    pinpai VARCHAR(2),
    chandi VARCHAR(2)
)
SELECT * FROM shangpin;
INSERT INTO shangpin VALUES(1,‘康佳（KONKA）42英寸全高清液晶电视‘,1,1999,‘康佳‘,‘深圳‘);
INSERT INTO shangpin VALUES(2,‘索尼（SONY）4G手机（黑色）‘,2,3238,‘索尼‘,‘深圳‘);
INSERT INTO shangpin VALUES(3,‘海信（Hisense）55英寸智能手机‘,1,4199,‘海信‘,‘青岛‘);
INSERT INTO shangpin VALUES(4,‘联想（Lenovo）14.0英寸笔记本电脑‘,3,5499,‘联想‘,‘北京‘);
INSERT INTO shangpin VALUES(5,‘索尼（SONY）13.3英寸触控超级本‘,3,11499,‘索尼‘,‘天津‘);
INSERT INTO shangpin VALUES(11,‘索尼（SONY）60英寸全高清液晶电视‘,1,6999,‘索尼‘,‘北京‘);
INSERT INTO shangpin VALUES(12,‘联想（Lenovo）14.0英寸笔记本电脑‘,3,2999,‘联想‘,‘北京‘);
INSERT INTO shangpin VALUES(13,‘联想 双卡双待3G手机‘,2,988,‘联想‘,‘北京‘);
INSERT INTO shangpin VALUES(14,‘惠普（HP）黑白激光打印机‘,3,1169,‘惠普‘,‘天津‘);
CREATE TABLE chanpin(
    protype_id INT,
    protype_name VARCHAR(5)
)
SELECT * FROM chanpin;
INSERT INTO chanpin VALUES(1,‘家用电器‘);
INSERT INTO chanpin VALUES(2,‘手机数码‘);
INSERT INTO chanpin VALUES(3,‘电脑办公‘);
INSERT INTO chanpin VALUES(4,‘图书影响‘);
INSERT INTO chanpin VALUES(5,‘家居家具‘);
INSERT INTO chanpin VALUES(6,‘服装配饰‘);
INSERT INTO chanpin VALUES(7,‘个护化妆‘);
INSERT INTO chanpin VALUES(8,‘户外运动‘);
INSERT INTO chanpin VALUES(9,‘汽车用品‘);
INSERT INTO chanpin VALUES(10,‘食品酒水‘);
INSERT INTO chanpin VALUES(11,‘营养保健‘);
-- 第二题
CREATE TABLE emp(
    id INT,
    NAME VARCHAR(20),
    gender VARCHAR(2),
    birthday DATETIME,
    email VARCHAR(10),
    remark VARCHAR(50)
)
SELECT * FROM emp
ALTER TABLE emp ADD COLUMN age INT;
ALTER TABLE emp MODIFY COLUMN email VARCHAR(50);
ALTER TABLE emp DROP COLUMN remark;
ALTER TABLE emp CHANGE COLUMN NAME username VARCHAR(2);