真正能約拍的app做好的網(wǎng)站怎么優(yōu)化
MySQL
- 一、INSERT語句
- 二、REPLACE語句
- 三、UPDATE語句
- 四、delete和TRUNCATE語句
- 五、MySQL用戶授權
- 1、密碼策略
- 2、用戶授權和撤銷授權
一、INSERT語句
#在表里面插入數(shù)據(jù)：默認情況下，一次插入操作只插入一行
方式1：
INSERT [INTO] 表名 [(column [, column...])] VALUES(value [, value...]);
方式2：
insert [into] 表名 set 字段1=值1, 字段2=值2
#一次性插入多條記錄：
INSERT [INTO] table [(column [, column...])] VALUES(value [, value...]),(value [, value...])
注：
1、如果為每列都指定值，則表名后不需列出插入的列名
2、可以使用如下方式一次插入多行：insert into 表名[(列名,…)] select 語句
3、如果需要插入其他特殊字符，應該采用\轉義字符做前綴
示例：
mysql8.0 [chap04]>create table t1(-> id int primary key,-> name char(30) not null,-> birthday date-> );
mysql8.0 [chap04]>insert t1 values (1,'xiaoming',20000101);
mysql8.0 [chap04]>insert into t1 values (2,'xiaohong',20000102),(3,'xiaolan',20000103),(4,'xiaohei',20000104);
mysql8.0 [chap04]>insert into t1(id,name) values (5,'xiaolv'),(6,'xiaobai');
mysql8.0 [chap04]>insert into t1 set id=6,name='xiaozi';
二、REPLACE語句
replace語句的語法格式有三種語法格式。
語法格式1：replace [into] 表名 [（字段列表）] values （值列表）
語法格式2：replace [into] 目標表名[(字段列表1)] select (字段列表2) from 源表 where 條件表達式
語法格式3：replace [into] 表名 set 字段1=值1, 字段2=值2
REPLACE與INSERT語句區(qū)別：
replace語句的功能與insert語句的功能基本相同，不同之處在于：使用replace語句向表插入新記錄時，如果新記錄的主鍵值或者唯一性約束的字段值與已有記錄相同，則已有記錄先被刪除（注意：已有記錄刪除時也不能違背外鍵約束條件），然后再插入新記錄。
使用replace的最大好處就是可以將delete和insert合二為一(效果相當于更新)，形成一個原子操作，這樣就無需將delete操作與insert操作置于事務中了
mysql> replace into class values(2,'02班');
ERROR 1451 (23000): Cannot delete or update a parent row: a foreign key constraint fails (`db1`.`student`, CONSTRAINT `student_ibfk_1` FOREIGN KEY (`c_num`) REFERENCES `class` (`cnum`))
mysql> replace into class values(3,'03班');
Query OK, 2 rows affected (0.01 sec)mysql8.0 [chap04]>replace t1 (id,name,birthday) values (8,'xiaoqing',20010101);
mysql8.0 [chap04]>replace t1 values(5,'xiaolv',20000105);
mysql8.0 [chap04]>select * from t1;
+----+----------+------------+
| id | name | birthday |
+----+----------+------------+
| 1 | xiaoming | 2000-01-01 |
| 2 | xiaohong | 2000-01-02 |
| 3 | xiaolan | 2000-01-03 |
| 4 | xiaohei | 2000-01-04 |
| 5 | xiaolv | 2000-01-05 |
| 6 | xiaobai | NULL |
| 7 | xiaozi | NULL |
| 8 | xiaoqing | 2001-01-01 |
+----+----------+------------+
mysql8.0 [chap04]>replace t1(id,name,birthday) values (9,'zhouyi',20010102),(10,'zhouer',20010102);
三、UPDATE語句
UPDATE 表名
SET column = value [, column = value]
[WHERE condition];
修改可以一次修改多行數(shù)據(jù)，修改的數(shù)據(jù)可用where子句限定，where子句里是一個條件表達式，只有符合該條件的行才會被修改。沒有where子句意味著where字句的表達式值為true。也可以同時修改多列，多列的修改中間采用逗號(,)隔開。
mysql8.0 [chap04]>select * from t1;
+----+----------+------------+
| id | name | birthday |
+----+----------+------------+
| 1 | xiaoming | 2000-01-01 |
| 2 | xiaohong | 2000-01-02 |
| 3 | xiaolan | 2000-01-03 |
| 4 | xiaohei | 2000-01-04 |
| 5 | xiaolv | 2000-01-05 |
| 6 | xiaobai | NULL |
| 7 | xiaozi | NULL |
| 8 | xiaoqing | 2001-01-01 |
| 9 | zhouyi | 2001-01-02 |
| 10 | zhouer | 2001-01-02 |
+----+----------+------------+
10 rows in set (0.00 sec)mysql8.0 [chap04]>update t1 set birthday=20010101 where id=6;
Query OK, 1 row affected (0.01 sec)
Rows matched: 1 Changed: 1 Warnings: 0
四、delete和TRUNCATE語句
DELETE FROM table_name [where 條件];
TRUNCATE TABLE table_name事物處理
beign;
delete from t1;
select * from t1;
rollback;
DROP、TRUNCATE、DELETE的區(qū)別：
-
delete：刪除數(shù)據(jù)，保留表結構，可以回滾，如果數(shù)據(jù)量大，很慢。
-
truncate： 刪除所有數(shù)據(jù)，保留表結構，不可以回滾，一次全部刪除所有數(shù)據(jù)，速度相對很快。
-
drop： 刪除數(shù)據(jù)和表結構，刪除速度最快。
mysql8.0 [chap04]>delete from t1 where id=7;
Query OK, 1 row affected (0.00 sec)
mysql8.0 [chap04]>create table t2 select * from t1;
mysql8.0 [chap04]>truncate table t2;
五、MySQL用戶授權
1、密碼策略
#mysql8.0會生成臨時密碼，查看臨時密碼
[root@mysql8-0-30 ~]# awk '/temporary password/ {print $NF}' /var/log/mysqld.log
[root@mysql8-0-30 ~]# grep 'password' /var/log/mysqld.log
#查看數(shù)據(jù)庫當前密碼策略：
mysql8.0 [chap03]>show VARIABLES like "%password%";
2、用戶授權和撤銷授權
MySql8有新的安全要求，不能像之前的版本那樣一次性創(chuàng)建用戶并授權。需要先創(chuàng)建用戶，再進行授權操作。
mysql8.0 [chap03]>grant all privileges on *.* to 'xiaoming'@'%';
ERROR 1410 (42000): You are not allowed to create a user with GRANT
1、創(chuàng)建用戶
#創(chuàng)建新用戶，語法：create user 'username'@'host' identified by 'password';
說明：username為自定義的用戶名，host為客戶端的域名或者IP，如果host為'%'時表示為任意IP，password為密碼。
mysql8.0 [mysql]>create user xiaoming@'%' identified by '123';
mysql8.0 [mysql]>select user,host,authentication_string from mysql.user;
#刪除用戶
mysql8.0 [mysql]>drop user xiaoming@'%';
#注意，如果刪除用戶時顯示如下提示，需要執(zhí)行該語句【mysql8.0 [(none)]>grant system_user on *.* to root@'%';】
mysql8.0 [mysql]>drop user xiaoming;
ERROR 1227 (42000): Access denied; you need (at least one of) the SYSTEM_USER privilege(s) for this operation
2、授權和回收權限
授予權限的原則：
- （1）只授予能滿足需要的最小權限 ，防止用戶干壞事。比如用戶只是需要查詢，那就只給 select 權限就可以了，不要給用戶賦予update 、 insert 或者 delete 權限
- （2）創(chuàng)建用戶的時候限制用戶的登錄主機 ，一般是限制成指定 IP 或者內網(wǎng) IP 段。
- （3）為每個用戶設置滿足密碼復雜度的密碼 。
- （4）定期清理不需要的用戶 ，回收權限或者刪除用戶。
#查看授予用戶的權限
mysql8.0 [mysql]>show grants;
mysql8.0 [mysql]>show grants for root@'%';
mysql8.0 [mysql]>select * from mysql.user;
#查看某個用戶從哪個服務器ip地址連接對某個數(shù)據(jù)庫的操作權限，這三個字段的組合構成了db表的主鍵。
mysql8.0 [mysql]>select * from mysql.db;
#查看用戶對單個表的權限
mysql8.0 [mysql]>select * from mysql.tables_priv;
授權語法：grant 權限列表 on 庫名.表名 to 用戶名@'主機' [with GRANT option];
| mysql用戶常用權限列表 | 說明 |
|---|---|
| all 或者all privileges | 授予用戶所有權限 |
| create | 授予用戶創(chuàng)建新數(shù)據(jù)庫和表的權限 |
| drop | 授予用戶刪除數(shù)據(jù)庫和表的權限 |
| delete | 授予用戶刪除表中的行的權限 |
| alter | 授予用戶修改表結構的權限 |
| insert | 授予用戶在表中插入行（add）的權限 |
| select | 授予用戶運行select命令以從表中讀取數(shù)據(jù)的權限 |
| update | 授予用戶更新表中的數(shù)據(jù)的權限 |
mysql8.0 [mysql]>grant all privileges on *.* to 'xiaoming'@'%' with grant option;
mysql8.0 [mysql]>flush privileges;
#說明：*.*中第一個*表示所有數(shù)據(jù)庫，第二個*表示所有數(shù)據(jù)表;with grant option表示授予xiaoming用戶grant命令（該命令可以給別的用戶授權）的權限
mysql8.0 [mysql]>select user,grant_priv from mysql.user;
+------------------+------------+
| user | grant_priv |
+------------------+------------+
| root | Y |
| xiaoming | Y |
| mysql.infoschema | N |
| mysql.session | N |
| mysql.sys | N |
+------------------+------------+
mysql8.0 [mysql]>create user xiaohong@'%' identified by '123';
Query OK, 0 rows affected (0.01 sec)mysql8.0 [mysql]>select select_priv,user from mysql.user;
+-------------+------------------+
| select_priv | user |
+-------------+------------------+
| Y | root |
| N | xiaohong |
| Y | xiaoming |
| Y | mysql.infoschema |
| N | mysql.session |
| N | mysql.sys |
+-------------+------------------+
6 rows in set (0.00 sec)mysql8.0 [mysql]>grant select on mysql.user to xiaohong@'%';
mysql8.0 [mysql]>select * from tables_priv;
+-----------+-------+---------------+------------+--------------------+---------------------+------------+-------------+
| Host | Db | User | Table_name | Grantor | Timestamp | Table_priv | Column_priv |
+-----------+-------+---------------+------------+--------------------+---------------------+------------+-------------+
| % | mysql | xiaohong | user | xiaoming@localhost | 2023-02-08 00:56:32 | Select | |
| localhost | mysql | mysql.session | user | boot@ | 2023-02-05 18:30:53 | Select | |
| localhost | sys | mysql.sys | sys_config | root@localhost | 2023-02-05 18:30:53 | Select | |
+-----------+-------+---------------+------------+--------------------+---------------------+------------+-------------+
mysql8.0 [mysql]>select * from db where user='xiaohong';
+------+--------+----------+-------------+-------------+-------------+-------------+-------------+-----------+------------+-----------------+------------+------------+-----------------------+------------------+------------------+----------------+---------------------+--------------------+--------------+------------+--------------+
| Host | Db | User | Select_priv | Insert_priv | Update_priv | Delete_priv | Create_priv | Drop_priv | Grant_priv | References_priv | Index_priv | Alter_priv | Create_tmp_table_priv | Lock_tables_priv | Create_view_priv | Show_view_priv | Create_routine_priv | Alter_routine_priv | Execute_priv | Event_priv | Trigger_priv |
+------+--------+----------+-------------+-------------+-------------+-------------+-------------+-----------+------------+-----------------+------------+------------+-----------------------+------------------+------------------+----------------+---------------------+--------------------+--------------+------------+--------------+
| % | chap03 | xiaohong | Y | N | N | N | N | N | N | N | N | N | N | N | N | N | N | N | N | N | N |
+------+--------+----------+-------------+-------------+-------------+-------------+-------------+-----------+------------+-----------------+------------+------------+-----------------------+------------------+------------------+----------------+---------------------+--------------------+--------------+------------+--------------+
mysql8.0 [mysql]>show grants for xiaohong@'%';
+--------------------------------------------------+
| Grants for xiaohong@% |
+--------------------------------------------------+
| GRANT USAGE ON *.* TO `xiaohong`@`%` |
| GRANT SELECT ON `chap03`.* TO `xiaohong`@`%` |
| GRANT SELECT ON `mysql`.`user` TO `xiaohong`@`%` |
+--------------------------------------------------+
#usage：連接（登錄）權限，建立一個用戶，就會自動授予usage權限（默認授予）。該usage權限并不能被revoke（回收）。#收回權限(不包含賦權權限)
REVOKE ALL PRIVILEGES ON *.* FROM username;
#收回賦權權限
REVOKE GRANT OPTION ON *.* FROM username;
mysql8.0 [(none)]>revoke grant option on *.* from xiaoming@'%';
Query OK, 0 rows affected (0.00 sec)mysql8.0 [(none)]>select grant_priv,user from mysql.user;
+------------+------------------+
| grant_priv | user |
+------------+------------------+
| Y | root |
| N | xiaohong |
| N | xiaoming |
| N | mysql.infoschema |
| N | mysql.session |
| N | mysql.sys |
+------------+------------------+
mysql8.0 [(none)]>revoke all on *.* from xiaoming;
#操作完后重新刷新權限
mysql8.0 [(none)]>flush privileges;
mysql8.0 [(none)]>revoke select on mysql.user from xiaohong;