mysqld 升級到8以上遇到的問題

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! d: F9 Y0 ?' D9 [- Mphp連到mysql出現2行errors : (discuz網頁出現的是連接到mysql錯誤表格,需自行寫一隻連接mysql的php程式來測試)
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mysqli_real_connect(): Server sent charset (255) unknown to the client. Please, report to the developers
% G; f( J1 I4 y, x* ]5 X, `mysqli_real_connect(): (HY000/2054): Server sent charset unknown to the client. Please, report to the developers
原因:
在MySQL 8.0.21中，caching_sha2_password是默認的身份驗證插件，而不是以往的mysql_native_password。所以和php不相容。可以降級php，也可以修改MySQL的配置。 吾人決定修改MySQL的配置:
% @. u1 V4 U, d( Avi /etc/my.cnf  加入下列:
[mysqld]
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1 Q; ?0 T3 Y1 mcharacter-set-server=utf8
default_authentication_plugin=mysql_native_password
2 C$ G6 g5 M$ r5 Xvalidate_password.policy=LOW
' g# ~1 d# d% R# n[mysql]
7 G0 ^& V8 ?' Tdefault-character-set=utf8

3 C$ S5 r( n/ u6 v, S7 s[client]
& t  p) Z& R% x8 J& ?8 F' `9 v3 ]default-character-set=utf8

/ o' c1 d0 M4 S然後重啟mysqld
service mysqld restart
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2 u0 ^/ @& V5 @4 f重啟後可能須做下列動作:
( O; c' v" \2 l) X1 |mysql -u roor -p  
SHOW VARIABLES LIKE 'validate_password%';
% I7 ~9 \& J+ ~; @; A' J. A% ISET GLOBAL validate_password_policy=LOW;ALTER USER 'root'@'localhost' IDENTIFIED WITH mysql_native_password BY '你的密碼';搞定!!

, s; U- G: V  L# C0 k; k3 p7 d2 i註: mysqld啟動時,在/var/log/mysql/mysqld.log紀錄著:註: 可以先寫支php程式以測試 ~~~
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1. <?
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2. $hostname = "x.x.x.x";
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3. $database = "db_name";
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4. $username = "user_name";
   
5. $password = "pwd";
   
6. 
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7. $conn = mysqli_connect($hostname, $username, $password,$database) or trigger_error(mysql_error(),E_USER_ERROR);
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8. mysqli_query($conn ,"SET NAMES utf8");
   
9. 
   
10. $sql = "select count(*) as total from " .  "table_name";
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11. $rec = mysqli_fetch_assoc(mysqli_query( $conn,$sql));
    
12. echo $rec['total'];
    
13. mysqli_close($conn);
    
14. ?>

複製代碼

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當php 7.2.24  connect to mysql server,出現 :

1. PHP Fatal error:  Uncaught Error: Call to undefined function mysqli_connect() in /test/connectmysql8.php:9
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2. Stack trace:
   
3. #0 {main}
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4.   thrown in /test/connectmysql8.php on line 9
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5. 
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6. Fatal error: Uncaught Error: Call to undefined function mysqli_connect() in /test/connectmysql8.php:9
   
7. Stack trace:
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8. #0 {main}
   
9.   thrown in /test/connectmysql8.php on line 9

複製代碼

這是版本相依的問題,只要 yum install php-mysqlnd  或 yum install php-mysqli 即可

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/ y0 S: v9 M/ \7 h& Z' {[Warning] [MY-013242] [Server] --character-set-server: 'utf8' is currently an alias for the character set UTF8MB3, but will be an alias for UTF8MB4 in a future release. Please consider using UTF8MB4 in order to be unambiguous.
  i( Z! M5 d" v! _- P1 n說明: 千萬不能照它建議用"UTF8MB4",否則無法成功啟動

(2)
. M. w* \7 o+ y& A# f; j4 b- F: B(1064) You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'system>0' at line 1
1 U4 ^6 f" X* A8 }SELECT COUNT(*) FROM common_usergroup WHERE type='special' and system>0
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(1064) You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'groups = '' AND starttime<=1532077291 AND (endtime>=1532077291 OR endtime=0) ORD' at line 1
SELECT * FROM forum_announcement WHERE type!=2 AND groups = '' AND starttime<=1532077291 AND (endtime>=1532077291 OR endtime=0) ORDER BY displayorder, starttime DESC, id DESC LIMIT 1
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+ p0 @/ N; i& {: s8 q+ n' D5 |! c因為MySQL 8.0+將system和groups作為了關鍵字，所以不能直接在SQL中將system和groups這兩個詞作為數據庫、數據表、數據表字段中的任意一種使用，如果數據庫名或數據表名或數據表字段名使用了system或groups作為名字，必須使用一對反引號引用起來。寫作`system`或`groups`。
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/ z: X- s$ ~$ t+ y3 [第一個錯誤需要找到Discuz!目錄中的source\class\table\table_common_usergroup.php，
& c- b1 D' U) n8 p7 [將文件中所有的system全部改成`system`，保存後重新上傳到服務器的相同目錄即可。
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第二個錯誤需要找到Discuz!目錄下中的source\class\table\table_forum_announcement.php，
# b' I6 A, S$ ^6 ^9 e& V- V' W" ]將文件中所有的groups全部改為`groups`，保存後重新上傳到服務器的相同目錄即可。

如果在MySQL 8+環境下安裝Discuz!，在安裝前需要給install\data\install.sql文件中沒有加引號的所有system逐一添加一對反引號保存重新上傳到服務器的相同目錄，否則也會出現SQL語法錯誤。

為了避免語法錯誤，在寫SQL語句時，一定要為所有的數據庫名、數據表名、數據表字段名全部添加一對反引號，像Discuz!這樣的寫法是很不妥的。
% d  ?% {5 l  H以上參考:   升級到 MySQL 8.0+ 後Discuz! 更新緩存時出現SQL語法錯誤
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