創(chuàng)建表：
CREATE TABLE teacher(
id CHAR(5) PRIMARY KEY,
name varchar(20) NOT NULL,
gender enum('man','women') NOT NULL,
poisition enum('助教‘,'講師','客服'
);
插入
INSERT INTO（表民）VALUES（內(nèi)容）
普通插入
INSERT INTO `teachers` VALUES('12','12','MAN','講師');
指定插入
insert into `teachers` ('id','gender','name') values('0511','man','hello')
插入多行數(shù)據(jù)
insert into `teachers`
values ('111','nihao','man'),
('222','www','women'),
('333','nnn','man');
修改
update `teachers` set `position` = '講師’ where `id`= '05110'
查詢
select * from `teachers` where 1
* 代表列
where 后面代表行
select 'name','gender' from `teachers` where 1;
指定行查詢
select `name` from `teachers` where `position`= '講師';
select `name` from `teachers` where `position`= '講師' or `position` = '教授';
select `name` from `teachers` where (`position`= '講師' or `position` = '教授') and `gender` = `man`;
優(yōu)先級(jí)問(wèn)題
排序：
select `name` from `teachers` where (`position`= '講師' or `position` = '教授') and `gender` = `man` order by `id` desc(降序）
多條件排序：
select `name` from `teachers` where (`position`= '講師' or `position` = '教授') and `gender` = `man` order by `id` desc，name;
分組查詢：
GROUP BY 通常不和order by 一起使用矩屁，group by通常是配合聚合函數(shù)一起使用豆瘫。
select `name` from `teachers` where 1 group by `gender`
select count(*) from `teachers` where 1 group by `gender`; 計(jì)數(shù)
select `gender`,count(*) from `teachers` where 1 group by `gender`
別名
select `gender` as `GENDER`,count(*) as `num` from `teachers` where 1 group by `gender`
刪除
delete from `teacher` where 1 全刪！宏怔！跑路吧坊谁。篓吁。
delete from `teacher` where `name` = 'caoliang'
在刪除之前一定要確認(rèn)where ，同時(shí)牡辽，需要在相同的where條件先select一次喳篇。！态辛！
連接：可以解決80%的問(wèn)題麸澜，還有一種是子查詢
1.內(nèi)連接
第一張表的每一行，和第二張表的每一列都連接一次奏黑。
Paste_Image.png
select a.id,a.name from 'class' as a
inner join 'student' as b
on a.id= b.id
where b.id=9
2.外連接
主要有左連接和右連接炊邦，在寫(xiě)語(yǔ)句時(shí)，寫(xiě)在前面的表叫左表熟史，后面的叫右表馁害。left join 是保持左邊不變，right是保持右邊不變蹂匹。
select a.id,a.name from 'class' as a
left join 'student' as b
on a.id= b.id
