mysqld 升級到8以上遇到的問題

coav4u

(1)
php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
mysqli_real_connect(): (HY000/2054): Server sent charset unknown to the client. Please, report to the developers
% i# U: J8 d& [  Y* _原因:
0 K. \) u( M9 z8 i* ]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]
9 W$ N7 l7 T6 N' l: R0 d
* |% }! p' @7 ycharacter-set-server=utf8
default_authentication_plugin=mysql_native_password
2 g' \4 k4 y* q& U+ M( Evalidate_password.policy=LOW
- u, |2 K, @- E# m7 i! M[mysql]
3 \+ c; y) M( `' k6 Ydefault-character-set=utf8

4 M  y$ Y  q+ [( ~: o& i' e5 l% y[client]
" r6 t& P8 N! \8 Ldefault-character-set=utf8
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3 i3 \9 J: O% f& w5 n1 j然後重啟mysqld
service mysqld restart
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# q$ b+ v! X0 ^- e$ k1 m: M/ g, b' I重啟後可能須做下列動作:
/ M5 e2 ~- }, l  [* ]3 o- F; \mysql -u roor -p  
$ X1 C9 i+ v" i: x1 v# W3 qSHOW VARIABLES LIKE 'validate_password%';
+ Z) p/ \% n- nSET 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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8 ]4 I! H$ V- R" \* K' @+ K& M* Z0 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 ~~~
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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";
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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);
   
8. mysqli_query($conn ,"SET NAMES utf8");
   
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));
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12. echo $rec['total'];
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13. mysqli_close($conn);
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14. ?>

複製代碼

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" b2 q- }' K9 Y* S/ `
) S' N7 X* O: [; \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
   
2. Stack trace:
   
3. #0 {main}
   
4.   thrown in /test/connectmysql8.php on line 9
   
5. 
   
6. Fatal error: Uncaught Error: Call to undefined function mysqli_connect() in /test/connectmysql8.php:9
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7. Stack trace:
   
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.
, }0 @6 `4 `# e2 {' d說明: 千萬不能照它建議用"UTF8MB4",否則無法成功啟動

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! Q! [6 Z+ V/ l5 R7 k(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
0 n9 ?) w) G2 ]% f5 Q! Y* ISELECT COUNT(*) FROM common_usergroup WHERE type='special' and system>0

(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
' b  ~4 u& W% R) G; L: V+ dSELECT * 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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& N# n+ ]$ [6 q+ f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`。

- q% L; T; E' t9 z6 S2 j第一個錯誤需要找到Discuz!目錄中的source\class\table\table_common_usergroup.php，
. u( V' h4 E9 \$ y9 F. o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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0 X# }5 I; @. [第二個錯誤需要找到Discuz!目錄下中的source\class\table\table_forum_announcement.php，
3 ^3 G, u+ Q6 u, y& a, z3 ~) q( B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。
, [5 S8 k# l) n' P以上參考:   升級到 MySQL 8.0+ 後Discuz! 更新緩存時出現SQL語法錯誤