mysqld 升級到8以上遇到的問題

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! o$ J9 f$ Q8 U, `& z5 A- K+ P1 Xphp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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- {: u* G  T4 J4 ~mysqli_real_connect(): Server sent charset (255) unknown to the client. Please, report to the developers
+ c0 L5 M# I  E9 Nmysqli_real_connect(): (HY000/2054): Server sent charset unknown to the client. Please, report to the developers
4 D+ Z( J1 U' c- w原因:
; o  r  z- E; h" C7 [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:
vi /etc/my.cnf  加入下列:
[mysqld]

2 T6 W- S0 c4 J' Z( |- \character-set-server=utf8
3 Q. ~& A  T% Z  }, Z, vdefault_authentication_plugin=mysql_native_password
validate_password.policy=LOW
[mysql]
  N  o+ ]# H9 {0 s  G, qdefault-character-set=utf8

( n3 y% d5 {; S' ^  [[client]
default-character-set=utf8
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然後重啟mysqld
service mysqld restart

' ~9 j* j' x" G) @$ ?* X重啟後可能須做下列動作:
( T7 w5 @) q  N2 G. [mysql -u roor -p  
+ E0 A; C) c6 o6 y; g) z3 m3 B: pSHOW VARIABLES LIKE 'validate_password%';
9 C' B0 j( r9 ?# V8 h1 \0 xSET GLOBAL validate_password_policy=LOW;ALTER USER 'root'@'localhost' IDENTIFIED WITH mysql_native_password BY '你的密碼';搞定!!

* {) D  E" o! g! i3 m; P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 ~~~

1. <?
   
2. $hostname = "x.x.x.x";
   
3. $database = "db_name";
   
4. $username = "user_name";
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5. $password = "pwd";
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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:
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3. #0 {main}
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4.   thrown in /test/connectmysql8.php on line 9
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5. 
   
6. Fatal error: Uncaught Error: Call to undefined function mysqli_connect() in /test/connectmysql8.php:9
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7. Stack trace:
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8. #0 {main}
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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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[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.
/ z: o8 y2 M; g" j% g說明: 千萬不能照它建議用"UTF8MB4",否則無法成功啟動

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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 'system>0' at line 1
SELECT COUNT(*) FROM common_usergroup WHERE type='special' and system>0
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* _# ~/ V' F" u$ W8 C(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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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`。

第一個錯誤需要找到Discuz!目錄中的source\class\table\table_common_usergroup.php，
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。

第二個錯誤需要找到Discuz!目錄下中的source\class\table\table_forum_announcement.php，
2 B: p7 Z6 R* f# q/ E+ ?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。

( H; d8 P% c+ `) B/ Z+ p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。
% B& u  ~) V' [. d2 w  t& o: M' s% m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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