php连接数据库都没问题,升级到10.10这后, 突然连接不上了. 这个问题放了很久, 今天突然搜索到一篇文章.
用链接的方式解决了. 原文如下:
So you installed Ubuntu, got all excited about developing your Rails application on it, and then…
No such file or directory - /tmp/mysql.sock)
No matter what you do, database connection doesn’t work. You reinstall Rails (of course you installed it via “sudo apt-get rails”, right??), reinstall MySql, recreate the database schema, change root’s password, install Kubuntu instead of Ubuntu… But it doesn’t work.
The reason for this error is quite simple, really: somewhere along Ruby’s Mysql driver, mysql socket is expected to exist at /tmp/mysql.sock. But that’s not where it is in Ubuntu. If you take some time searching, you’ll notice that the .sock file is actually on /var/run/mysqld - and it’s called mysqld.sock instead.
In fact, if you Google it, there is a closed bug entry on Rails’ tracking system regarding that problem, and the suggested solution there is to change your database.yml to add a link to the correct socket. Something like:
production: adapter: mysql socket: /var/run/mysqld/mysqld.sock
Which is obviously not a good idea, since you’ll end up creating new projects, moving to a different OS or whatever - and everything will break again.
So I tried a small patchwork to fool mysql’s driver, and then it works nicely:
sudo ln -s /var/run/mysqld/mysqld.sock /tmp/mysql.sock
That way you will actually HAVE a /tmp/mysql.sock file, as expected by mysql driver, and everything will connect just fine. Just like it’s meant to be. Amen!

mySqlStringTypesimpactStorageAndPerformanCeaseAsfollows:1)長度,始終使用theSamestoragespace,whatcanbefasterbutlessspace-felfficity.2)varCharisvariable varcharisvariable length,morespace-morespace-morespace-effficitybuteftife buteftife butfority butfority textifforlyslower.3)

mysqlStringTypesIncludeVarChar,文本,char,Enum和set.1)varCharisVersAtileForvariable-lengthStringStringSuptoPuptOuptoPepePecifiedLimit.2)textisidealforlargetStortStorStoverStoverStorageWithoutAutAdefinedLength.3)charlisfixed-lenftenge,for forConsistentDatalikeCodes.4)

MySQLoffersvariousstringdatatypes:1)CHARforfixed-lengthstrings,2)VARCHARforvariable-lengthtext,3)BINARYandVARBINARYforbinarydata,4)BLOBandTEXTforlargedata,and5)ENUMandSETforcontrolledinput.Eachtypehasspecificusesandperformancecharacteristics,sochoose

TograntpermissionstonewMySQLusers,followthesesteps:1)AccessMySQLasauserwithsufficientprivileges,2)CreateanewuserwiththeCREATEUSERcommand,3)UsetheGRANTcommandtospecifypermissionslikeSELECT,INSERT,UPDATE,orALLPRIVILEGESonspecificdatabasesortables,and4)

toadduserInmysqleffect和securly,跟隨台詞:1)USEtheCreateUserStattoDaneWuser,指定thehostandastrongpassword.2)GrantNecterAryAryaryPrivilegesSustherthing privilegesgeStatement,usifementStatement,adheringtotheprinciplelastprefilegege.3)

toaddanewuserwithcomplexpermissionsinmysql,loldtheSesteps:1)創建eTheEserWithCreateuser'newuser'newuser'@''localhost'Indedify'pa ssword';。 2)GrantreadAccesstoalltablesin'mydatabase'withGrantSelectOnMyDatabase.to'newuser'@'localhost';。 3)GrantWriteAccessto'

MySQL中的字符串數據類型包括CHAR、VARCHAR、BINARY、VARBINARY、BLOB、TEXT,排序規則(Collations)決定了字符串的比較和排序方式。 1.CHAR適合固定長度字符串,VARCHAR適合可變長度字符串。 2.BINARY和VARBINARY用於二進制數據,BLOB和TEXT用於大對像數據。 3.排序規則如utf8mb4_unicode_ci忽略大小寫,適合用戶名;utf8mb4_bin區分大小寫,適合需要精確比較的字段。

最佳的MySQLVARCHAR列長度選擇應基於數據分析、考慮未來增長、評估性能影響及字符集需求。 1)分析數據以確定典型長度;2)預留未來擴展空間;3)注意大長度對性能的影響;4)考慮字符集對存儲的影響。通過這些步驟,可以優化數據庫的效率和擴展性。


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