mysqld 升級到8以上遇到的問題

coav4u

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; b# X8 M1 M+ R0 c6 X9 Y  uphp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)

mysqli_real_connect(): Server sent charset (255) unknown to the client. Please, report to the developers
- f6 Y/ l' s. h+ Y" d7 qmysqli_real_connect(): (HY000/2054): Server sent charset unknown to the client. Please, report to the developers
/ R4 M3 V  M3 n4 k; e# ^5 T5 Z原因:
! R( J" m  n, P0 }& x* h( v2 K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:
: l% t; t: m& F; E0 t) s5 Hvi /etc/my.cnf  加入下列:
[mysqld]

, Z6 M2 d! E% Vcharacter-set-server=utf8
default_authentication_plugin=mysql_native_password
validate_password.policy=LOW
* i$ m/ X" a( T7 Q0 M& C6 y[mysql]
default-character-set=utf8
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[client]
* f1 ]  g# \' l! `default-character-set=utf8
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* O0 \6 ~: e( t, N( Y1 E+ ?8 r! Z然後重啟mysqld
service mysqld restart
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重啟後可能須做下列動作:
mysql -u roor -p  
0 i" A. P) p, s0 n! ]  f, VSHOW VARIABLES LIKE 'validate_password%';
* Q& ?8 t7 Q; LSET GLOBAL validate_password_policy=LOW;ALTER USER 'root'@'localhost' IDENTIFIED WITH mysql_native_password BY '你的密碼';搞定!!
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$ v2 K( b1 [/ t3 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 ~~~

1. <?
   
2. $hostname = "x.x.x.x";
   
3. $database = "db_name";
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4. $username = "user_name";
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5. $password = "pwd";
   
6. 
   
7. $conn = mysqli_connect($hostname, $username, $password,$database) or trigger_error(mysql_error(),E_USER_ERROR);
   
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'];
    
13. mysqli_close($conn);
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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. 
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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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[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.
說明: 千萬不能照它建議用"UTF8MB4",否則無法成功啟動

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& o6 X5 v6 ^! [0 g9 B2 J7 L(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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$ x) i8 }5 L* v0 t3 V* w" W0 x(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
" H/ B6 ^9 M, \8 XSELECT * 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

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，
# X, m; p& n7 a1 p, ?' w( a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。

- V$ i7 c) v1 M! E- m第二個錯誤需要找到Discuz!目錄下中的source\class\table\table_forum_announcement.php，
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。
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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。
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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