mysqld 升級到8以上遇到的問題

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/ y8 K$ _3 ?1 o; Q( b: Zphp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
mysqli_real_connect(): (HY000/2054): Server sent charset unknown to the client. Please, report to the developers
原因:
) [2 |* O3 a# W" ?$ m  `4 y( @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:
2 m2 P* c, e8 C+ m2 t/ E" Y0 j6 Cvi /etc/my.cnf  加入下列:
; {- k# y8 {6 S% _* n9 i[mysqld]
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character-set-server=utf8
3 }; G5 j; }- A; tdefault_authentication_plugin=mysql_native_password
9 F% \: i* g. m1 @$ a: N2 ~: X9 pvalidate_password.policy=LOW
5 F6 x) K) q& a/ ~4 d2 k[mysql]
default-character-set=utf8
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9 J) ?7 x1 F0 u! g3 P9 I4 A[client]
default-character-set=utf8

然後重啟mysqld
9 K" L6 e7 ~: l2 ?: bservice mysqld restart

重啟後可能須做下列動作:
2 G! D) X6 @& p8 emysql -u roor -p  
7 Q+ y7 j) ~  q% `SHOW VARIABLES LIKE 'validate_password%';
SET GLOBAL validate_password_policy=LOW;ALTER USER 'root'@'localhost' IDENTIFIED WITH mysql_native_password BY '你的密碼';搞定!!

: _# C! T$ h. K/ U: }$ k) C+ ?: b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";
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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");
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9. 
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10. $sql = "select count(*) as total from " .  "table_name";
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11. $rec = mysqli_fetch_assoc(mysqli_query( $conn,$sql));
    
12. echo $rec['total'];
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13. mysqli_close($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. 
   
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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* q, q# D7 j- Q0 j" Q[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.
& o0 ^4 B, A+ W+ v說明: 千萬不能照它建議用"UTF8MB4",否則無法成功啟動
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7 |$ k5 T# `6 g+ ?( W$ ]. d2 Z! f(2)
4 D4 d' c7 Z# z6 j) O$ r. G(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

: z& d4 E4 F. K; E0 Q(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
* V  S9 l5 ?, ~+ V$ {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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8 p$ o' [. a  u" X. ~. A. t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`。

3 j5 }5 j' A3 F- B0 z' E1 {' Z; M第一個錯誤需要找到Discuz!目錄中的source\class\table\table_common_usergroup.php，
# {! [7 v+ o2 Y; ]; Y, C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。

* N/ C& b6 h" w第二個錯誤需要找到Discuz!目錄下中的source\class\table\table_forum_announcement.php，
: x' j# U' B9 l9 u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。

* N/ V5 S  L  k: q- i% `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。
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. g9 U' q  B7 W8 C5 I6 Y2 t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。
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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