-- 創(chuàng)建數(shù)據(jù)庫
create database if not exists school default charset=utf8;
-- 使用數(shù)據(jù)庫
use school;
-- 創(chuàng)建表格
creat table studentinfo (
id int primary key auto_increment ,
name varchar(20) ,
sex char ,
age int ,
address varchar(100)
);
-- 查看數(shù)據(jù)表
show tables;
-- 插入數(shù)據(jù)
insert into studentinfo (name ,sex,age , address) values ("賈寶玉","男"舞终，18伙判，"北平")，
("賈政", "男", 40 ,"浙江")迹鹅，("晴雯"担孔，"女"江锨，20,"四川")，("襲人","女",29,"貴州"),
("薛寶釵","女",19,"北平")糕篇，("林黛玉"啄育，"女"，19拌消，"浙江")挑豌；
-- 查看數(shù)據(jù) 通配符 * 表示所有
select * from studentinfo;
-- 手動(dòng)寫出字段 全量查詢
select id, name ,sex , age ,address from studentinfo;
-- 只查詢指定的數(shù)據(jù)列
select id, name ,sex from studentinfo;
-- 條件查詢
selecct * from studentinfo where sex='女';
-- 根據(jù)查詢結(jié)果排序 order by
select * grom studentinfo order by age aesc;
-- 顯示查詢結(jié)果的條數(shù)
select * from studentinfo limit 3 ;
-- 復(fù)合
select * from studentinfo where sex='女' order by age desc limit 3;
-- 別名 AS as 可以省略
select id as 編號(hào) ,name as 姓名安券，sex as 性別 ，age as 年齡氓英， address as 地址 from studentinfo侯勉；
select id 編號(hào)，name 姓名铝阐， sex 性別址貌，age 年齡 ，address 地址 studentinfo;
-- 單條件查詢
select * from studentinfo where age<20;
select * from studentinfo where age is not null;
-- 多條件查詢
-- 不等于
select * from studentinfo where age!=20;
select * from studentinfo where age<>20;
select * from studentinfo where not (age=20);
-- 與 或
select * from studentinfo where age >20 && sex='女';
select * from studentinfo where age >20 and sex='女';
select * from studentinfo where age >20 || sex='女';
select * from studentinfo where age >20 or sex='女';
-- 去重 去除重復(fù)的數(shù)據(jù)
select distinct name,sex,age,address from studentinfo;
