增删改查语句
增删改查的语句命令为
增:insert
删:delete
改:update
查:SELECT或者show
库操作
创建数据库:create database shujukuba; 创建带字符集的数据库:create database mydb2 CHARACTER SET=utf8; 创建带校验的数据库:create database mydb3 CHARACTER SET=utf8 COLLATE utf8_general_ci; 显示数据库:show databases; 删除数据库:DROP DATABASE shujukuba; 修改数据库编码:ALTER DATABASE shujukuba character set gb2312;
表操作
创建数据库表(创建一个表名为:employee,该表中含有id、name、sex、birthday、job字段):
create table employee ( id int, name varchar(40), sex char(4), birthday date, job varchar(100), );
表中增加image字段:alter table employee add image blob; 修改job值,使其长度为60(原长度为1000):alter table employee modify job varchar(60); 删除sex列:alter table employee drop sex; 表名改为user(原名employee):rename table employee to user; 修改表的字符集为utf-8:alter table user character set utf8; 列name修改为username:alter table user change column name username varchar(100); 删除表:drop table user;
增删改查实例
准备表
新建表employee:
create table employee ( id int, name varchar(40), sex varchar(4), birthday date, entry_date date, salary decimal(8,2), resume text );
插入表数据
插入数据:
insert into employee(id,name,sex,birthday,entry_date,salary,resume) values(1,'zhangsan','male','1993-03-04','2016-11-10','1000','i am a developer');
指定某些列插入数据:insert into employee(id) values(6); 插入汉字:insert into employee(id,name) values(6,'张三');
修改表数据:
将所有员工薪水修改为5000元:update employee set salary=5000; 将姓名为’zs’的员工薪水修改为3000元:update employee set salary = 3000 where name='zhangsan'; 将姓名为’aaa’的员工薪水修改为4000元,job改为ccc:update employee set salary = 4000,job='ccc' where name='张三'; 将wu的薪水在原有基础上增加1000元:update employee set salary = salary+1000 where name='张三';
删除表数据
删除表中名称为“zs”的记录:delete from employee where job='ccc'; 删除表中所有记录:delete from employee; 使用truncate删除表中记录:truncate table employee;
查询表数据
查询表中所有学生的信息:select id,name,chinese,english,math from student; 查询表中所有学生的姓名和对应的英语成绩:select name,english from student; 查询姓名为wu的学生成绩:select * from student where name='张三'; 查询英语成绩大于90分的同学:select * from student where english>'90'; 查询英语分数在 80-90之间的同学:select * from student where english>=80 and english=<90;
常见的MySQL语句命令
进入mysql 命令行:mysql -uroot -p; 查看所有数据库:show databases; 创建数据库:create database niu charset utf8; 删除数据库:drop database niu; 选择数据库:use databases; 查看所有表:show tables; 查看创建数据库的语句:show create database databasename; 查看创建表的语句:show create table tablename; 查看表结构:desc tablenmae;
常见MySQL字段含义
自增长:auto_increment 非空:not null 默认值:default 唯一:unique 指定字符集:charset 主键:primary key