MySQL操作指令與內建函式總結
阿新 • • 發佈：2018-12-11
MySQL常用操作指令和內建函式，歡迎留言補充！
- 建庫，選擇庫
create database class1824;
use python1804;
- 刪庫
drop database class1824;
3.建表，刪表
create table user(userid int(11),username varchar(32),password char(32));
drop table user;
- 改表名
alter table user rename users;
- 表字段改名
alter table user change userid id int(11);
- 修改欄位型別與位置
alter table user modify username char(32) first;
- 新增刪除表字段
alter table user add column password char(64) after username;
alter table user drop column sex;
- create建立索引，create 不能建立主鍵索引，注意與alter的區別
create index in_id on t1(id);
- alter建立索引，create 不能建立主鍵索引，注意與alter的區別
alter table users add unique(欄位名 ); #fulltext(欄位名 );primary key(欄位名 );index(欄位名)
- 刪除索引
alter table users drop index username on t1;
- 刪除主鍵索引，先取消遞增
alter table users modify id int(11) unsigned not null;
alter table users drop primary key;
- 插入資料方法一，所有欄位，順序一致
insert into users values(1,"haha","adfdsfadsf12"),(2,"xixi","afdsf123321");
- 插入資料方法二，設定了遞增的欄位可不操作
insert into users(id,username,password) values(3,"hehe","12333adf123");
- 替換列資料
update scores set nu=replace(nu,1,2);
- 去重
select distinct balance from money;
- 排序，desc降序，asc升序。
select * from money where age>30 order by balance desc,age asc limit 2 ,5;
asc升序；
17.分組，group by
select count(province),province from money group by province;
18.條件篩選group by
select count(province) as result,province from money group by province with rollup;
19.條件篩選group by
select count(province) as result,province from money group by province having result>1;
20.表聯合查詢
select user.username as '使用者名稱',order_goods.oid,order_goods.name as "商品名" from user,order_goods where user.uid=order_goods.uid;
21.表聯合查詢2
select user.username as '使用者',order_goods.name as "商品" from user inner join order_goods on user.uid=order_goods.uid;
22.left join 語法
select * from user left join order_goods on user.uid=order_goods.uid;
23.注意與22的去區別
select * from user where uid in(select uid from order_goods);
select uid from user union all select uid from order_goods;
24.更新資料update
update user set username="哈哈",password="123456" where uid=8;
25.同時對兩個表更新
update money m,users u set m.balance=m.balance*u.id,u.password=m.balance where m.id=u.id;
26.delete from，累加id從原來的基礎上累加，如1，2，3，將id=2刪除了,id=3不變！注意與27中truncate的區別
delete from money where id>9;
delete from 表名；
- truncate清空表以後 id 從1 開始
truncate table users;
28.資料庫遠端連線,注意符號*的使用
grant 許可權 on 庫名.表名 to '使用者名稱'@'ip地址' identified by 密碼；
grant all on *.* to 'root'@'localhost' identified by '123456' with grant option;
grant select,insert on class1824.* to 'jinxingping'@'localhost' identified by '123321';
flush privileges;
service mysql restart；
29.刪除指定許可權
revoke insert on class1824.* from 'jinxingping'@'localhost';
30.複製表結構和資料
create table user1 like users；
insert into user1 select * from users；
31.表檢視 view
create view v_t1 as select * from t1 where id>2 and id<8; show create/drop view v_t1;
- mysql常用內建函式
mysql 顯示內容 用 select
字串函式
mysql> select concat("hello","world") as nihao; #拼接字串
select lcase("MYSQL");#轉小寫
select ucase("mysql"); #轉大寫
mysql> select length("haha"); 字串的長度
mysql> select ltrim(" haha"); 去除左側空格
+-------------------+
| ltrim(" haha") |
+-------------------+
| haha |
+-------------------+
1 row in set (0.00 sec)
mysql> select rtrim(" haha ");去除右側空格
mysql> select repeat("重要的事情說三遍",6);
select replace("java 是世界上最好的語言","java","python");
mysql> select substr("python is so good",2,7); 從第二個字元開始 擷取7個 mysql 從1開始
mysql> select concat(space(20),'haha'); #生成20個空格
數學函式
mysql> select ceiling(123.1);
mysql> select floor(123.1);
mysql> select rand(); 求隨機數 0-1之間的小數
mysql> select bin(10);
日期函式
mysql> select curdate(); 返回日期 2018-7-25
mysql> select curtime(); 11:21:33
mysql> select now(); 日期+時間 2018-07-25 11:22:14
mysql> select week(now()); 返回29 表示當前第幾周
mysql> select year(now()); 返回2018
mysql> select unix_timestamp(now()); 當前時間的時間戳
mysql> select from_unixtime(1532489069);
+---------------------------+
| from_unixtime(1532489069) |
+---------------------------+
| 2018-07-25 11:24:29 |
+---------------------------+ 將當前的時間戳格式化為日期