MySQL 權限和查詢緩存
MySQL 權限和查詢緩存mysql
================================================================================sql
概述：數據庫
本章將主要介紹MySQL數據庫中的權限和查詢緩存，具體內容以下：vim
MySQL的權限類別；centos
·數據類權限：庫級別、表級別、字段級別；緩存
·管理類權限；bash
·程序類權限；服務器
MySQL用戶管理：ide
·用戶帳號；函數
·建立、重命名、刪除、修改用戶密碼
忘記管理員密碼的解決辦法：
受權：GRANT
·建立、查看及取消受權
查詢緩存
·查詢緩存相關的服務器變量：
·統計緩存數據狀態變量：
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MySQL用戶和權限管理
1.權限類別
★用戶帳號：user@host
user：帳戶名稱；
host：此帳戶可經過哪些客戶端主機請求建立鏈接線程；
%：任意長度的任意字符；
_：任意單個字符；
★MySQL權限類別：
※數據類權限：
庫級別：把某個數據庫的全部權限或某些權限受權給指定用戶（數據庫級別的）；
表級別：把一個數據庫中的某個表或有限的幾個表受權給指定用戶；
字段級別：把一個表上指定的字段受權給指定用戶；
※管理類：如改變服務器變量的值等；
※程序類：可否調用或執行函數，程序代碼等程序；
☉管理類：
CREATE USER； //建立用戶
RELOAD； //能夠使mysql關閉日誌文件，滾動日誌文件並打開新文件
LOCK TABLES；
REPLICATION CLIENT， REPLICATION SLAVE；
SHUTDOWN； //關閉mysql服務器進程的權限
FILE； //從文件中加載數據的權限
SHOW DATABASES；
PROCESS； //查看進程
SUPER //不受控制的任何管理功能等權限
☉程序類：
FUNCTION（存儲函數），PROCEDURE（存儲過程），TRIGGER（觸發器）
操做：CREATE，ALTER，DROP，EXECUTE（執行）
☉庫和表級別：
CREATE，ALTER，DROP
INDEX
CREATE VIEW
SHOW VIEW
GRANT：受權
OPTION：可以把本身得到的權限生成一個副本轉贈給其它用戶；
☉數據操做權限：
◆表：
INSERT/DELETE/UPDATE/SELECT
◆字段：
SELECT(col1,col2,...)
UPDATE(col1,col2,...)
INSERT(col1,col2,...)
☉全部權限：
ALL
ALL PRIVILEGES
★元數據數據庫（數據字典）：mysql
☉受權相關的表：
db, host, user
tables_priv, column_priv, procs_priv, proxies_priv
MariaDB [(none)]> use mysql; Reading table information for completion of table and column names You can turn off this feature to get a quicker startup with -A Database changed MariaDB [mysql]> SHOW TABLES; +---------------------------+ | Tables_in_mysql | +---------------------------+ | columns_priv | # 字段級別的權限 | db | # 庫級別的權限表 | event | | func | | general_log | | help_category | | help_keyword | | help_relation | | help_topic | | host | # 主機鏈接限制 | ndb_binlog_index | | plugin | | proc | | procs_priv | # 程序級別的權限 | proxies_priv | # 代理權限 | servers | | slow_log | | tables_priv | # 表級別的權限 | time_zone | | time_zone_leap_second | | time_zone_name | | time_zone_transition | | time_zone_transition_type | | user | # 用戶帳號表 +---------------------------+ 24 rows in set (0.00 sec)
2.MySQL用戶管理：
★用戶帳號：user@host
user：帳戶名稱；
host：此帳戶可經過哪些客戶端主機請求建立鏈接線程;（IP,主機名，NETWORK）
%：任意長度的任意字符；
_：任意單個字符；
注意：
基於主機名受權和IP地址受權是兩個不一樣的帳號，若是基於主機名受權時會反解主機名到IP地址，通常不建議，而且要跳過主機名解析
★skip_name_resolve={ON|OFF}
是否跳過主機名解析
★建立用戶：
CREATE USER 'user'@'host' [IDENTIFIED BY [PASSWORD] 'password'] [,'user'@'host' [IDENTIFIED BY [PASSWORD] 'password']...]
★重命名：RENAME USER
RENAME USER old_user TO new_user[, old_user TO new_user] ...
★刪除用戶：
DROP USER 'user'@'host' [, 'user'@'host'] ...
★修改用戶密碼
SET PASSWORD [FOR 'user'@'host'] = PASSWORD('cleartext password');
UPDATE mysql.user SET Password=PASSWORD('cleartext password') WHERE User='USERNAME' AND Host='HOST';
mysqladmin -uUSERNAME -hHOST -p password 'NEW_PASS'
☉FLUSH PRIVILEGES
通知mysql進程重讀受權表
演示：
1.能夠使用SHOW PROCESSLIST 查看當前線程列表，以下：
MariaDB [hellodb]> SHOW PROCESSLIST; +----+---------+-----------------+---------+---------+------+-------+------------------+----------+ | Id | User | Host | db | Command | Time | State | Info | Progress | +----+---------+-----------------+---------+---------+------+-------+------------------+----------+ | 3 | root | localhost | hellodb | Query | 0 | NULL | SHOW PROCESSLIST | 0.000 | | 4 | rsyslog | 127.0.0.1:38101 | Syslog | Sleep | 123 | | NULL | 0.000 | +----+---------+-----------------+---------+---------+------+-------+------------------+----------+ 2 rows in set (0.00 sec)
2.建立用戶，修改密碼，修改用戶名，並查看剛建立用戶的權限
# 建立用戶帳號及密碼 MariaDB [(none)]> CREATE USER 'tao'@'192.168.1.%' IDENTIFIED BY '134296'; Query OK, 0 rows affected (0.00 sec)
# 修改用戶帳戶密碼，並重讀受權表
MariaDB [(none)]> SET PASSWORD FOR 'tao'@'192.168.1.%' = PASSWORD('123456');
Query OK, 0 rows affected (0.00 sec)
MariaDB [(none)]> FLUSH PRIVILEGES;
Query OK, 0 rows affected (0.01 sec)
# 修改用戶名 MariaDB [(none)]> RENAME USER 'tao'@'192.168.1.%' TO 'xiu'@'192.168.1.%'; Query OK, 0 rows affected (0.02 sec)
# 並查看剛建立用戶的權限，發現爲usage MariaDB [(none)]> SHOW GRANTS FOR 'xiu'@'192.168.1.%'; +--------------------------------------------------------------------------------------------------------------+ | Grants for xiu@192.168.1.% | +--------------------------------------------------------------------------------------------------------------+ | GRANT USAGE ON *.* TO 'xiu'@'192.168.1.%' IDENTIFIED BY PASSWORD '*6BB4837EB74329105EE4568DDA7DC67ED2CA2AD9' | +--------------------------------------------------------------------------------------------------------------+ 1 row in set (0.00 sec)
3.登陸建立的用戶帳戶，建立數據庫，能夠發現權限不被容許，可見新建立的用戶幾乎是沒有任何權限的；要想有權限就須要給用戶授予相關的管理、程序、數據類的權限等
[root@centos7 ~]# mysql -uxiu -h192.168.1.107 -p123456 Welcome to the MariaDB monitor. Commands end with ; or \g. Your MariaDB connection id is 6 Server version: 5.5.44-MariaDB MariaDB Server Copyright (c) 2000, 2015, Oracle, MariaDB Corporation Ab and others. Type 'help;' or '\h' for help. Type '\c' to clear the current input statement. MariaDB [(none)]> SHOW DATABASES; +--------------------+ | Database | +--------------------+ | information_schema | | test | +--------------------+ 2 rows in set (0.05 sec) MariaDB [test]> CREATE DATABASE mydb; ERROR 1044 (42000): Access denied for user 'xiu'@'192.168.1.%' to database 'mydb'
4.要想有權限就須要給用戶授予相關的管理、程序、數據類的權限等，授予xiu用戶相關的權限以下：
MariaDB [(none)]> GRANT ALL ON mydb.* TO 'xiu'@'192.168.1.%'; # 授予全部的權限 Query OK, 0 rows affected (0.00 sec) MariaDB [(none)]> SHOW GRANTS FOR 'xiu'@'192.168.1.%'; +--------------------------------------------------------------------------------------------------------------+ | Grants for xiu@192.168.1.% | +--------------------------------------------------------------------------------------------------------------+ | GRANT USAGE ON *.* TO 'xiu'@'192.168.1.%' IDENTIFIED BY PASSWORD '*6BB4837EB74329105EE4568DDA7DC67ED2CA2AD9' | | GRANT ALL PRIVILEGES ON `mydb`.* TO 'xiu'@'192.168.1.%' | +--------------------------------------------------------------------------------------------------------------+ 2 rows in set (0.00 sec) MariaDB [(none)]> REVOKE UPDATE ON mydb.* FROM 'xiu'@'192.168.1.%'; # 回收UPDATE權限 Query OK, 0 rows affected (0.00 sec) MariaDB [(none)]> SHOW GRANTS FOR 'xiu'@'192.168.1.%'; +-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+ | Grants for xiu@192.168.1.% | +-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+ | GRANT USAGE ON *.* TO 'xiu'@'192.168.1.%' IDENTIFIED BY PASSWORD '*6BB4837EB74329105EE4568DDA7DC67ED2CA2AD9' | | GRANT SELECT, INSERT, DELETE, CREATE, DROP, REFERENCES, INDEX, ALTER, CREATE TEMPORARY TABLES, LOCK TABLES, EXECUTE, CREATE VIEW, SHOW VIEW, CREATE ROUTINE, ALTER ROUTINE, EVENT, TRIGGER ON `mydb`.* TO 'xiu'@'192.168.1.%' | +-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+ 2 rows in set (0.00 sec)
3.忘記管理員密碼的解決辦法：
★解決步驟以下：
(1)啓動mysqld進程時，使用--skip-grant-tables和--skip-networking選項；
CentOS 7：mariadb.service
CentOS 6：/etc/init.d/mysqld
(2)經過UPDATE命令修改管理員密碼；
(3)以正常方式啓動mysqld進程；
演示：
1.以CentOS 7 爲例，首先查看mysql數據庫user表中有關用戶的帳戶名和密碼以下：
MariaDB [(none)]> SELECT user,host,password FROM mysql.user; +------------+-------------+-------------------------------------------+ | user | host | password | +------------+-------------+-------------------------------------------+ | root | localhost | *41EE0F8759D5340036B009143E1727DB5787A448 | | root | centos7 | *41EE0F8759D5340036B009143E1727DB5787A448 | | root | 127.0.0.1 | *41EE0F8759D5340036B009143E1727DB5787A448 | | root | ::1 | *41EE0F8759D5340036B009143E1727DB5787A448 | | ultraxuser | 127.0.0.1 | *41EE0F8759D5340036B009143E1727DB5787A448 | | ultraxuser | localhost | *41EE0F8759D5340036B009143E1727DB5787A448 | | rsyslog | 127.0.0.1 | *41EE0F8759D5340036B009143E1727DB5787A448 | | rsyslog | local | *41EE0F8759D5340036B009143E1727DB5787A448 | | zbxuser | 10.1.%.% | *24E65C3D3577DA6C2A596788CEAA02923A74B75D | | zbxuser | 127.0.0.1 | *24E65C3D3577DA6C2A596788CEAA02923A74B75D | | xiu | 192.168.1.% | *6BB4837EB74329105EE4568DDA7DC67ED2CA2AD9 | +------------+-------------+-------------------------------------------+
2.假如如今我忘記了root管理員用戶的密碼，執行過程以下：
1）首先關閉mysql服務，修改啓動mariadb.service的文件，添加 --skip-grant-tables和--skip-networking選項，以下：
[root@centos7 ~]# systemctl stop mariadb.service # 中止mariadb服務 [root@centos7 ~]# vim /usr/lib/systemd/system/mariadb.service # 修改mariadb啓動文件 ExecStart=/usr/bin/mysqld_safe --basedir=/usr --skip-grant-tables --skip-networking //在ExecStart 後添加 [root@centos7 ~]# systemctl daemon-reload # 要想生效須要重載
2）再次啓動mariadb服務，而後使用mysql直接鏈接，鏈接成功後使用UPDATE修改密碼
[root@centos7 ~]# mysql
Welcome to the MariaDB monitor. Commands end with ; or \g.
Your MariaDB connection id is 2
Server version: 5.5.44-MariaDB MariaDB Server
Copyright (c) 2000, 2015, Oracle, MariaDB Corporation Ab and others.
Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.
MariaDB [(none)]> UPDATE mysql.user SET Password=PASSWORD('taoxiu') WHERE User='root'; # 修改密碼
Query OK, 4 rows affected (0.00 sec)
Rows matched: 4 Changed: 4 Warnings: 0
MariaDB [(none)]> exit
Bye
3）而後再次關閉mariadb服務，把mariadb啓動文件中添加的--skip-grant-tables和--skip-networking選項刪除便可
[root@centos7 ~]# systemctl stop mariadb.service [root@centos7 ~]# vim /usr/lib/systemd/system/mariadb.service ExecStart=/usr/bin/mysqld_safe --basedir=/usr # 把添加的選項刪除便可 [root@centos7 ~]# systemctl daemon-reload [root@centos7 ~]# systemctl start mariadb.service [root@centos7 ~]# mysql # 再使用mysql直接登陸，發現已經登陸不上了 ERROR 1045 (28000): Access denied for user 'root'@'localhost' (using password: NO) [root@centos7 ~]# mysql -uroot -ptaoxiu # 使用修改的密碼成功登陸 Welcome to the MariaDB monitor. Commands end with ; or \g. Your MariaDB connection id is 3 Server version: 5.5.44-MariaDB MariaDB Server Copyright (c) 2000, 2015, Oracle, MariaDB Corporation Ab and others. Type 'help;' or '\h' for help. Type '\c' to clear the current input statement. MariaDB [(none)]>
4.受權：GRANT
★GRANT
priv_type [(column_list)] [, priv_type [(column_list)]] ... //權限類型（字段）
ON [object_type] priv_level
TO user_specification [, user_specification] ... 指明用戶名、主機、密碼（存在的話就不須要了），一次可受權多個
[REQUIRE {NONE | ssl_option [[AND] ssl_option] ...}]
[WITH with_option ...]
★查看受權：SHOW GRANTS
SHOW GRANTS [FOR 'user'@'host']
★取消受權：REVOKE
☉REVOKE
priv_type [(column_list)][, priv_type [(column_list)]] ...
ON [object_type] priv_level
FROM 'user'@'host' [, 'user'@'host'] ...
☉REVOKE ALL PRIVILEGES, GRANT OPTION
FROM user [, user] ...
演示：
1.建立tao用戶帳戶，並指定密碼；
MariaDB [mysql]> CREATE USER 'tao'@'localhost' IDENTIFIED BY '123456'; Query OK, 0 rows affected (0.01 sec) MariaDB [mysql]> SHOW GRANTS FOR 'tao'@'localhost'; +------------------------------------------------------------------------------------------------------------+ | Grants for tao@localhost | +------------------------------------------------------------------------------------------------------------+ | GRANT USAGE ON *.* TO 'tao'@'localhost' IDENTIFIED BY PASSWORD '*6BB4837EB74329105EE4568DDA7DC67ED2CA2AD9' | +------------------------------------------------------------------------------------------------------------+ 1 row in set (0.00 sec)
2.授予tao用戶全部權限；
MariaDB [(none)]> GRANT ALL ON mydb.* TO 'tao'@'localhost'; Query OK, 0 rows affected (0.01 sec) MariaDB [(none)]> SHOW GRANTS FOR 'tao'@'localhost'; +------------------------------------------------------------------------------------------------------------+ | Grants for tao@localhost | +------------------------------------------------------------------------------------------------------------+ | GRANT USAGE ON *.* TO 'tao'@'localhost' IDENTIFIED BY PASSWORD '*6BB4837EB74329105EE4568DDA7DC67ED2CA2AD9' | | GRANT ALL PRIVILEGES ON `mydb`.* TO 'tao'@'localhost' | +------------------------------------------------------------------------------------------------------------+ 2 rows in set (0.00 sec)
3.如今我再建立一個叫'jing'的用戶，看讓tao用戶可否把本身的權限轉增給jing用戶，以下：
MariaDB [(none)]> CREATE USER 'jing'@'localhost'; # 在root管理員上建立jing用戶 Query OK, 0 rows affected (0.00 sec) [root@centos7 ~]# mysql -utao -hlocalhost -p123456 # 登陸tao用戶帳號 Welcome to the MariaDB monitor. Commands end with ; or \g. Your MariaDB connection id is 10 Server version: 5.5.44-MariaDB MariaDB Server Copyright (c) 2000, 2015, Oracle, MariaDB Corporation Ab and others. Type 'help;' or '\h' for help. Type '\c' to clear the current input statement. MariaDB [(none)]> show databases; # 能夠看到受權的mydb數據庫 +--------------------+ | Database | +--------------------+ | information_schema | | mydb | | test | +--------------------+ 3 rows in set (0.01 sec) # tao用戶把本身的權限轉贈給jing用戶，發現失敗，這是由於要想有轉贈的權限，須要管理員授予WITH GRANT OPTION權限 MariaDB [(none)]> GRANT SELECT,INSERT,DELETE on mydb.* TO 'jing'@'localhost'; ERROR 1044 (42000): Access denied for user 'tao'@'localhost' to database 'mydb'
4.管理員授予tao用戶容許轉贈的權限，再次測試能夠發現能夠成功轉贈給jing用戶
MariaDB [(none)]> GRANT ALL ON mydb.* TO 'tao'@'localhost' WITH GRANT OPTION; Query OK, 0 rows affected (0.00 sec) MariaDB [(none)]> FLUSH PRIVILEGES; Query OK, 0 rows affected (0.00 sec) # --------------------------------------------------------------------------------------- # 登陸tao用戶帳號，查看其權限能夠發現多了一項 WITH GRANT OPTION 的權限， MariaDB [(none)]> SHOW GRANTs FOR 'tao'@'localhost'; +------------------------------------------------------------------------------------------------------------+ | Grants for tao@localhost | +------------------------------------------------------------------------------------------------------------+ | GRANT USAGE ON *.* TO 'tao'@'localhost' IDENTIFIED BY PASSWORD '*6BB4837EB74329105EE4568DDA7DC67ED2CA2AD9' | | GRANT ALL PRIVILEGES ON `mydb`.* TO 'tao'@'localhost' WITH GRANT OPTION | +------------------------------------------------------------------------------------------------------------+ 2 rows in set (0.00 sec) # 成功將本身的權限轉贈給jing用戶 MariaDB [(none)]> GRANT SELECT,INSERT,DELETE on mydb.* TO 'jing'@'localhost'; Query OK, 0 rows affected (0.00 sec)
5.收回tao用戶的GRANT OPTION的權限
MariaDB [(none)]> REVOKE GRANT OPTION ON mydb.* FROM 'tao'@'localhost'; # 回收權限 Query OK, 0 rows affected (0.00 sec) MariaDB [(none)]> SHOW GRANTS FOR 'tao'@'localhost'; +------------------------------------------------------------------------------------------------------------+ | Grants for tao@localhost | +------------------------------------------------------------------------------------------------------------+ | GRANT USAGE ON *.* TO 'tao'@'localhost' IDENTIFIED BY PASSWORD '*6BB4837EB74329105EE4568DDA7DC67ED2CA2AD9' | | GRANT ALL PRIVILEGES ON `mydb`.* TO 'tao'@'localhost' | +------------------------------------------------------------------------------------------------------------+ 2 rows in set (0.00 sec)
6.如今受權tao用戶hellodb數據庫的stuents表上某個字段的受權，以下：
MariaDB [(none)]> GRANT SELECT(Name,Age),UPDATE(Age) ON hellodb.students TO 'tao'@'localhost'; Query OK, 0 rows affected (0.06 sec)
登陸tao的用戶帳號，查看權限，執行操做以下：
MariaDB [(none)]> SHOW GRANTS FOR 'tao'@'localhost'; # 查看權限以下： +------------------------------------------------------------------------------------------------------------+ | Grants for tao@localhost | +------------------------------------------------------------------------------------------------------------+ | GRANT USAGE ON *.* TO 'tao'@'localhost' IDENTIFIED BY PASSWORD '*6BB4837EB74329105EE4568DDA7DC67ED2CA2AD9' | | GRANT ALL PRIVILEGES ON `mydb`.* TO 'tao'@'localhost' | | GRANT SELECT (Age, Name), UPDATE (Age) ON `hellodb`.`students` TO 'tao'@'localhost' | +------------------------------------------------------------------------------------------------------------+ 3 rows in set (0.00 sec) MariaDB [(none)]> SHOW DATABASES; # 能夠看到數據庫中又多了一個hellodb的數據庫 +--------------------+ | Database | +--------------------+ | information_schema | | hellodb | | mydb | | test | +--------------------+ 4 rows in set (0.00 sec) MariaDB [(none)]> USE hellodb; Reading table information for completion of table and column names You can turn off this feature to get a quicker startup with -A Database changed MariaDB [hellodb]> SHOW TABLES; # 能夠發現僅能看見咱們受權給的students表 +-------------------+ | Tables_in_hellodb | +-------------------+ | students | +-------------------+ 1 row in set (0.05 sec) MariaDB [hellodb]> DESC students; # 表結構也只有Name和Age兩個受權的字段，其餘未受權的均不可見 +-------+---------------------+------+-----+---------+-------+ | Field | Type | Null | Key | Default | Extra | +-------+---------------------+------+-----+---------+-------+ | Name | varchar(50) | NO | | NULL | | | Age | tinyint(3) unsigned | NO | | NULL | | +-------+---------------------+------+-----+---------+-------+ 2 rows in set (0.08 sec) MariaDB [hellodb]> SELECT * FROM students; # 查詢全部的的字段發現不容許，由於其餘字段未經受權 ERROR 1143 (42000): SELECT command denied to user 'tao'@'localhost' for column 'StuID' in table 'students' MariaDB [hellodb]> SELECT Name,Age FROM students; # 只能查看受權的字段 +---------------+-----+ | Name | Age | +---------------+-----+ | Shi Zhongyu | 22 | | Shi Potian | 22 | | Xie Yanke | 53 | | Ding Dian | 32 | | Yu Yutong | 26 | | Shi Qing | 46 | | Xi Ren | 19 | | Lin Daiyu | 17 | | Ren Yingying | 20 | | Yue Lingshan | 19 | | Yuan Chengzhi | 23 | | Wen Qingqing | 19 | | Tian Boguang | 33 | | Lu Wushuang | 17 | | Duan Yu | 19 | | Xu Zhu | 21 | | Lin Chong | 25 | | Hua Rong | 23 | | Xue Baochai | 18 | | Diao Chan | 19 | | Huang Yueying | 22 | | Xiao Qiao | 20 | | Ma Chao | 23 | | Xu Xian | 27 | | Sun Dasheng | 100 | +---------------+-----+ 25 rows in set (0.00 sec) #----------------------------------------------------------------------------------- MariaDB [hellodb]> UPDATE students SET Age=21 WHERE Name='Duan YU'; # 能夠修改年齡 Query OK, 1 row affected (0.00 sec) Rows matched: 1 Changed: 1 Warnings: 0 MariaDB [hellodb]> UPDATE students SET Name=GuoJing WHERE Name='Duan YU'; # 修改姓名失敗，由於只受權了UPDATE容許修改Age字段 ERROR 1143 (42000): UPDATE command denied to user 'tao'@'localhost' for column 'Name' in table 'students' MariaDB [hellodb]> SELECT Name,Age FROM students; +---------------+-----+ | Name | Age | +---------------+-----+ | Shi Zhongyu | 22 | | Shi Potian | 22 | | Xie Yanke | 53 | | Ding Dian | 32 | | Yu Yutong | 26 | | Shi Qing | 46 | | Xi Ren | 19 | | Lin Daiyu | 17 | | Ren Yingying | 20 | | Yue Lingshan | 19 | | Yuan Chengzhi | 23 | | Wen Qingqing | 19 | | Tian Boguang | 33 | | Lu Wushuang | 17 | | Duan Yu | 21 | | Xu Zhu | 21 | | Lin Chong | 25 | | Hua Rong | 23 | | Xue Baochai | 18 | | Diao Chan | 19 | | Huang Yueying | 22 | | Xiao Qiao | 20 | | Ma Chao | 23 | | Xu Xian | 27 | | Sun Dasheng | 100 | +---------------+-----+ 25 rows in set (0.00 sec)
查詢緩存：
1.介紹
★緩存：k/v
key：查詢語句的hash值
value：查詢語句的執行結果
★如何判斷緩存是否命中：
經過查詢語句的哈希值判斷：哈希值考慮的因素包括
查詢自己；
要查詢數據庫；
客戶端使用的協議版本；
...
★哪些查詢可能不會被緩存？
查詢語句中包含UDF（用戶自定義函數）
存儲函數 如:CURRENT_TIME()
用戶自定義變量
臨時表
mysql系統表或者是包含列級別權限的查詢
有着不肯定結果值的函數(now())；
★附圖：
查詢執行過程
2.查詢緩存相關的服務器變量：
★query_cache_limit：
可以緩存的最大查詢結果；（單語句結果集大小上限）
有着較大結果集的語句，顯式使用 SQL_NO_CACHE，以免先緩存再移出；
★query_cache_min_res_unit：
內存塊的最小分配單位；緩存太小的查詢結果集會浪費內存空間；
較小的值會減小空間浪費，但會致使更頻繁地內存分配及回收操做；
較大值的會帶來空間浪費；
★query_cache_size：
查詢緩存空間的總共可用的大小；單位是字節，必須是1024的整數倍；
★query_cache_strip_comments
★query_cache_type：
緩存功能啓用與否；
ON：啓用；
OFF：禁用；
DEMAND：按需緩存，僅緩存SELECT語句中帶SQL_CACHE的查詢結果；
★query_cache_wlock_invalidate：
若是某表被其它鏈接鎖定，是否仍然能夠從查詢緩存中返回查詢結果；
默認爲OFF，表示能夠；ON則表示不能夠；
----------------------------------------------------------------------------
注意：
要想讓設定永久有效，要寫在配置文件當中
3.統計緩存數據狀態變量：
★查看命令：
mysql> SHOW GLOBAL STATUS LIKE 'Qcache%';
★命中率：
Qcache_hits/Com_select （命中次數/執行查詢語句的次數）
★查看SELECT語句的執行次數
mysql> SHOW STATUS LIKE 'Com_select '
演示：
1.查詢緩存相關的服務器變量
MariaDB [(none)]> SHOW VARIABLES LIKE '%query_cache%'; +------------------------------+---------+ | Variable_name | Value | +------------------------------+---------+ | have_query_cache | YES | //是否擁有緩存功能 | query_cache_limit | 1048576 | //單語句結果集上限，字節爲單位，默認大小爲1M | query_cache_min_res_unit | 4096 | //內存塊的最小分配單位 | query_cache_size | 0 | | query_cache_strip_comments | OFF | | query_cache_type | ON | //緩存功能是否啓用 | query_cache_wlock_invalidate | OFF | +------------------------------+---------+
2.設定緩存空間大小，並執行SELECT語句，查看緩存命中率等統計參數
# 設定緩存空間大小爲10M MariaDB [(none)]> SET GLOBAL query_cache_size=10485760; Query OK, 0 rows affected (0.00 sec) MariaDB [(none)]> SHOW VARIABLES LIKE '%query_cache%'; +------------------------------+----------+ | Variable_name | Value | +------------------------------+----------+ | have_query_cache | YES | | query_cache_limit | 1048576 | | query_cache_min_res_unit | 4096 | | query_cache_size | 10485760 | # 設置成功 | query_cache_strip_comments | OFF | | query_cache_type | ON | | query_cache_wlock_invalidate | OFF | +------------------------------+----------+ 7 rows in set (0.01 sec) MariaDB [(none)]> USE hellodb; Reading table information for completion of table and column names You can turn off this feature to get a quicker startup with -A Database changed MariaDB [hellodb]> SHOW STATUS LIKE 'Qcache%'; # 查看緩存統計變量 +-------------------------+----------+ | Variable_name | Value | +-------------------------+----------+ | Qcache_free_blocks | 1 | | Qcache_free_memory | 10468296 | | Qcache_hits | 0 | | Qcache_inserts | 0 | | Qcache_lowmem_prunes | 0 | | Qcache_not_cached | 1 | | Qcache_queries_in_cache | 0 | | Qcache_total_blocks | 1 | +-------------------------+----------+ 8 rows in set (0.01 sec) # 執行SELECT語句3次 MariaDB [hellodb]> SELECT Name,Age FROM students WHERE Age >= 20; +---------------+-----+ | Name | Age | +---------------+-----+ | Shi Zhongyu | 22 | | Shi Potian | 22 | | Xie Yanke | 53 | | Ding Dian | 32 | | Yu Yutong | 26 | | Shi Qing | 46 | | Ren Yingying | 20 | | Yuan Chengzhi | 23 | | Tian Boguang | 33 | | Duan Yu | 21 | | Xu Zhu | 21 | | Lin Chong | 25 | | Hua Rong | 23 | | Huang Yueying | 22 | | Xiao Qiao | 20 | | Ma Chao | 23 | | Xu Xian | 27 | | Sun Dasheng | 100 | +---------------+-----+ 18 rows in set (0.00 sec) MariaDB [hellodb]> SHOW STATUS LIKE 'Qcache%'; +-------------------------+----------+ | Variable_name | Value | +-------------------------+----------+ | Qcache_free_blocks | 1 | | Qcache_free_memory | 10466752 | | Qcache_hits | 2 | # 緩存命中2次 | Qcache_inserts | 1 | # 插入了一個緩存語句 | Qcache_lowmem_prunes | 0 | | Qcache_not_cached | 1 | | Qcache_queries_in_cache | 1 | | Qcache_total_blocks | 4 | +-------------------------+----------+ 8 rows in set (0.00 sec) # 查詢執行SELECT語句的次數 MariaDB [hellodb]> SHOW STATUS LIKE 'Com_select'; +---------------+-------+ | Variable_name | Value | +---------------+-------+ | Com_select | 5 | +---------------+-------+ 1 row in set (0.00 sec)
3.查看各類語句的執行次數，不能修改，能夠置零
MariaDB [(none)]> SHOW GLOBAL STATUS LIKE 'Com_%'; +----------------------------+-------+ | Variable_name | Value | +----------------------------+-------+ | Com_admin_commands | 0 | | Com_alter_db | 0 | | Com_alter_db_upgrade | 0 | | Com_alter_event | 0 | | Com_alter_function | 0 | | Com_alter_procedure | 0 | | Com_alter_server | 0 | | Com_alter_table | 0 | | Com_alter_tablespace | 0 | | Com_analyze | 0 | | Com_assign_to_keycache | 0 | | Com_begin | 157 | | Com_binlog | 0 | | Com_call_procedure | 0 | | Com_change_db | 5 | | Com_change_master | 0 | | Com_check | 0 | | Com_checksum | 0 | | Com_commit | 157 | | Com_create_db | 0 | | Com_create_event | 0 | | Com_create_function | 0 | | Com_create_index | 0 | | Com_create_procedure | 0 | | Com_create_server | 0 | | Com_create_table | 0 | | Com_create_trigger | 0 | | Com_create_udf | 0 | | Com_create_user | 2 | | Com_create_view | 0 | | Com_dealloc_sql | 0 | | Com_delete | 0 | | Com_delete_multi | 0 | | Com_do | 0 | | Com_drop_db | 0 | | Com_drop_event | 0 | | Com_drop_function | 0 | | Com_drop_index | 0 | | Com_drop_procedure | 0 | | Com_drop_server | 0 | | Com_drop_table | 0 | | Com_drop_trigger | 0 | | Com_drop_user | 0 | | Com_drop_view | 0 | | Com_empty_query | 0 | | Com_execute_sql | 0 | | Com_flush | 1 | | Com_grant | 6 | | Com_ha_close | 0 | | Com_ha_open | 0 | | Com_ha_read | 0 | | Com_help | 0 | | Com_insert | 207 | | Com_insert_select | 0 | | Com_install_plugin | 0 | | Com_kill | 0 | | Com_load | 0 | | Com_lock_tables | 0 | | Com_optimize | 0 | | Com_preload_keys | 0 | | Com_prepare_sql | 0 | | Com_purge | 0 | | Com_purge_before_date | 0 | | Com_release_savepoint | 0 | | Com_rename_table | 0 | | Com_rename_user | 0 | | Com_repair | 0 | | Com_replace | 0 | | Com_replace_select | 0 | | Com_reset | 0 | | Com_resignal | 0 | | Com_revoke | 1 | | Com_revoke_all | 0 | | Com_rollback | 0 | | Com_rollback_to_savepoint | 0 | | Com_savepoint | 0 | | Com_select | 27 | | Com_set_option | 2 | | Com_show_authors | 0 | | Com_show_binlog_events | 0 | | Com_show_binlogs | 0 | | Com_show_charsets | 0 | | Com_show_client_statistics | 0 | | Com_show_collations | 0 | | Com_show_contributors | 0 | | Com_show_create_db | 0 | | Com_show_create_event | 0 | | Com_show_create_func | 0 | | Com_show_create_proc | 0 | | Com_show_create_table | 0 | | Com_show_create_trigger | 0 | | Com_show_databases | 9 | | Com_show_engine_logs | 0 | | Com_show_engine_mutex | 0 | | Com_show_engine_status | 0 | | Com_show_errors | 0 | | Com_show_events | 0 | | Com_show_fields | 37 | | Com_show_function_status | 0 | | Com_show_grants | 9 | | Com_show_index_statistics | 0 | | Com_show_keys | 0 | | Com_show_master_status | 0 | | Com_show_open_tables | 0 | | Com_show_plugins | 0 | | Com_show_privileges | 0 | | Com_show_procedure_status | 0 | | Com_show_processlist | 0 | | Com_show_profile | 0 | | Com_show_profiles | 0 | | Com_show_relaylog_events | 0 | | Com_show_slave_hosts | 0 | | Com_show_slave_status | 0 | | Com_show_status | 4 | | Com_show_storage_engines | 0 | | Com_show_table_statistics | 0 | | Com_show_table_status | 0 | | Com_show_tables | 7 | | Com_show_triggers | 0 | | Com_show_user_statistics | 0 | | Com_show_variables | 3 | | Com_show_warnings | 0 | | Com_signal | 0 | | Com_slave_start | 0 | | Com_slave_stop | 0 | | Com_stmt_close | 0 | | Com_stmt_execute | 0 | | Com_stmt_fetch | 0 | | Com_stmt_prepare | 0 | | Com_stmt_reprepare | 0 | | Com_stmt_reset | 0 | | Com_stmt_send_long_data | 0 | | Com_truncate | 0 | | Com_uninstall_plugin | 0 | | Com_unlock_tables | 0 | | Com_update | 2 | | Com_update_multi | 0 | | Com_xa_commit | 0 | | Com_xa_end | 0 | | Com_xa_prepare | 0 | | Com_xa_recover | 0 | | Com_xa_rollback | 0 | | Com_xa_start | 0 | | Compression | OFF | +----------------------------+-------+ 144 rows in set (0.00 sec)
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