Mysql help命令（帮助信息）中文注解
在开发或测试环境在碰到mysql相关故障时，大多数朋友可能会通过论坛发帖，QQ群讨论方式来获取帮助。该方式是获取帮助的有效途径之一。然而如果在生产环境，在没有网络的环境下，这些方式就无助于问题的解决。无论何种数据库，从官方网站获取帮助是最直接最有效的方式。其次没有网络的环境下，我们可以通过MySQL客户端工具自带的帮助信息来解决问题。
1)MySQL官方手册
和Oracle官方文档一下，MySQL官方手册是获取MySQL帮助最直接最效的方式。该手册包含很多个部分，比如有关SQL的语法，MySQL安装方式，MySQL的系统变量，状态变量，命令行的常用工具，数据库的管等等。总之是一个MySQL数据相关的大合集。支持PDF及html方式下载。
下载位置：http://dev.mysql.com/doc/
2)MySQL客户端工具自带的帮助
获取mysql有关的帮助信息，直接在mysql提示符下输入help即可获得有关在mysql客户端相关的帮助信息。 这个方式与OracleSQL*plus下的help是类似的。 mysql>help ForinformationaboutMySQLproductsandservices,visit: http://www.mysql.com/ Fordeveloperinformation,includingtheMySQLReferenceManual,visit: http://dev.mysql.com/ TobuyMySQLEnterprisesupport,training,orotherproducts,visit: https://shop.mysql.com/ ListofallMySQLcommands: Notethatalltextcommandsmustbefirstonlineandendwith';' ?(\?)Synonymfor`help'. clear(\c)Clearthecurrentinputstatement.--清除当前输入的语句 connect(\r)Reconnecttotheserver.Optionalargumentsaredbandhost.--重新连接，通常用于被剔除或异常断开后重新连接，SQL*plus下也有这样一个connect命令 delimiter(\d)Setstatementdelimiter.--设置命令终止符，缺省为；，比如我们可以设定为/来表示语句结束 edit(\e)Editcommandwith$EDITOR.--编辑缓冲区的上一条SQL语句到文件，缺省调用vi，文件会放在/tmp路径下 ego(\G)Sendcommandtomysqlserver,displayresultvertically.--控制结果显示为垂直显示 exit(\q)Exitmysql.Sameasquit.--退出mysql go(\g)Sendcommandtomysqlserver.--发送命令到mysql服务 help(\h)Displaythishelp. nopager(\n)Disablepager,printtostdout.--关闭页设置，打印到标准输出 notee(\t)Don'twriteintooutfile.--关闭输出到文件 pager(\P)SetPAGER[to_pager].PrintthequeryresultsviaPAGER.--设置pager方式，可以设置为调用more,less等等，主要是用于分页显示 print(\p)Printcurrentcommand. prompt(\R)Changeyourmysqlprompt.--改变mysql的提示符 quit(\q)Quitmysql. rehash(\#)Rebuildcompletionhash.--自动补齐相关对象名字 source(\.)ExecuteanSQLscriptfile.Takesafilenameasanargument.--执行脚本文件 status(\s)Getstatusinformationfromtheserver.--获得状态信息 system(\!)Executeasystemshellcommand.--执行系统命令 tee(\T)Setoutfile[to_outfile].Appendeverythingintogivenoutfile.--操作结果输出到文件 use(\u)Useanotherdatabase.Takesdatabasenameasargument.--切换数据库 charset(\C)Switchtoanothercharset.Mightbeneededforprocessingbinlogwithmulti-bytecharsets.--设置字符集 warnings(\W)Showwarningsaftereverystatement.--打印警告信息 nowarning(\w)Don'tshowwarningsaftereverystatement. --上面的所有命令，扩号内的为快捷操作，即只需要输入“\”+字母即可执行 Forserversidehelp,type'helpcontents'--注意这里的描述helpcontents将获得服务器端的相关帮助信息 --演示部分，演示常用命令 --connect命令 mysql>connectchardblocalhost; Readingtableinformationforcompletionoftableandcolumnnames Youcanturnoffthisfeaturetogetaquickerstartupwith-A Connectionid:5 Currentdatabase:chardb --设置分页，在多余一个页面显示时会不停的翻滚，用该命令可以设置分页，设置为调用系统命令 mysql>pagermore--设置为more方式 PAGERsetto'more' mysql>selecttable_name,table_type,enginefrominformation_schema.tables;--该查询会超出一屏显示后按空格键会自动翻滚到下一屏 mysql>pagertail-5;--设置输出尾部5行 PAGERsetto'tail-5' mysql>selecttable_name,table_type,enginefrominformation_schema.tables; |setup_timers|BASETABLE|PERFORMANCE_SCHEMA| |threads|BASETABLE|PERFORMANCE_SCHEMA| |animals|BASETABLE|InnoDB| |shop|BASETABLE|InnoDB| +----------------------------------------------+-------------+--------------------+ 92rowsinset(0.02sec) mysql>pager;--查看当前的pager设置 PAGERsetto'tail-5' mysql>nopager;--切换到标准(缺省)pager方式 PAGERsettostdout --tee命令，输出日志文件 mysql>tee/tmp/query.log--开启输出到文件，相当与SQL*plus下的spool Loggingtofile'/tmp/query.log' mysql>selecttable_name,table_type,enginefrominformation_schema.tables; +----------------------------------------------+-------------+--------------------+ |table_name|table_type|engine| +----------------------------------------------+-------------+--------------------+ |CHARACTER_SETS|SYSTEMVIEW|MEMORY| |COLLATIONS|SYSTEMVIEW|MEMORY| ............. mysql>notee;--关闭输出到文件，相当于SQL*Plus下的spooloff Outfiledisabled. mysql>systemtail/tmp/query.log--查看输出的日志文件 |setup_consumers|BASETABLE|PERFORMANCE_SCHEMA| |setup_instruments|BASETABLE|PERFORMANCE_SCHEMA| |setup_timers|BASETABLE|PERFORMANCE_SCHEMA| |threads|BASETABLE|PERFORMANCE_SCHEMA| |animals|BASETABLE|InnoDB| |shop|BASETABLE|InnoDB| +----------------------------------------------+-------------+--------------------+ 92rowsinset(0.02sec) --改变mysql提示符 mysql>promptSessionA> PROMPTsetto'SessionA>' --恢复到缺省提示符 SessionA>prompt; ReturningtodefaultPROMPTofmysql> --执行sql脚本文件 mysql>systemmorequery.sql--注意，此时为当前目录 usechardb select*fromtb_isam; mysql>sourcequery.sql Readingtableinformationforcompletionoftableandcolumnnames Youcanturnoffthisfeaturetogetaquickerstartupwith-A Databasechanged +------+-------+ |id|value| +------+-------+ |1|a| |2|b| |3|c| |4|f| +------+-------+ 4rowsinset(0.00sec) --获取状态信息 mysql>status; -------------- mysqlVer14.14Distrib5.5.37,forLinux(x86_64)usingreadline5.1 Connectionid:6 Currentdatabase:chardb Currentuser:root@localhost SSL:Notinuse Currentpager:less Usingoutfile:'' Usingdelimiter:; Serverversion:5.5.37-logMySQLCommunityServer(GPL) Protocolversion:10 Connection:LocalhostviaUNIXsocket Servercharacterset:latin1 Dbcharacterset:utf8 Clientcharacterset:latin1 Conn.characterset:latin1 UNIXsocket:/var/lib/mysql/mysql.sock Uptime:3hours10min59sec Threads:1Questions:97Slowqueries:0Opens:313Flushtables:1Opentables:51Queriespersecondavg:0.008 -------------- --修改客户端字符集 mysql>charsetgbk; Charsetchanged mysql>\s -------------- mysqlVer14.14Distrib5.5.37,forLinux(x86_64)usingreadline5.1 Connectionid:6 Currentdatabase:chardb Currentuser:root@localhost SSL:Notinuse Currentpager:less Usingoutfile:'' Usingdelimiter:; Serverversion:5.5.37-logMySQLCommunityServer(GPL) Protocolversion:10 Connection:LocalhostviaUNIXsocket Servercharacterset:latin1 Dbcharacterset:utf8 Clientcharacterset:gbk---客户端和conn端字符集都变成gbk了。 Conn.characterset:gbk UNIXsocket:/var/lib/mysql/mysql.sock Uptime:3hours13min33sec Threads:1Questions:105Slowqueries:0Opens:313Flushtables:1Opentables:51Queriespersecondavg:0.009 -------------- mysql>warnings; Showwarningsenabled. mysql>selecs1; ERROR1064(42000):YouhaveanerrorinyourSQLsyntax;checkthemanualthatcorrespondstoyourMySQLserverversionfortherightsyntaxtousenear'selecs1'atline1 mysql>showwarnings; +-------+------+------------------------------------------------------------------------------------------------------------------------------------------------------------+ |Level|Code|Message| +-------+------+------------------------------------------------------------------------------------------------------------------------------------------------------------+ |Error|1064|YouhaveanerrorinyourSQLsyntax;checkthemanualthatcorrespondstoyourMySQLserverversionfortherightsyntaxtousenear'selecs1'atline1| +-------+------+------------------------------------------------------------------------------------------------------------------------------------------------------------+ 1rowinset(0.00sec) mysql>showerrors; +-------+------+------------------------------------------------------------------------------------------------------------------------------------------------------------+ |Level|Code|Message| +-------+------+------------------------------------------------------------------------------------------------------------------------------------------------------------+ |Error|1064|YouhaveanerrorinyourSQLsyntax;checkthemanualthatcorrespondstoyourMySQLserverversionfortherightsyntaxtousenear'selecs1'atline1| +-------+------+------------------------------------------------------------------------------------------------------------------------------------------------------------+ 1rowinset(0.00sec) mysql>nowarning; Showwarningsdisabled.
3、服务端的相关帮助
--获取服务器管理相关的帮助，输入helpcontents
mysql>helpcontents;
Youaskedforhelpabouthelpcategory:"Contents"
Formoreinformation,type'help<item>',where<item>isoneofthefollowing
categories:
AccountManagement
Administration
CompoundStatements
DataDefinition
DataManipulation
DataTypes
Functions
FunctionsandModifiersforUsewithGROUPBY
GeographicFeatures
HelpMetadata
LanguageStructure
Plugins
Procedures
StorageEngines
TableMaintenance
Transactions
User-DefinedFunctions
Utility
--要查询那一个部分的内容，直接输入help+内容，如下
mysql>helpadministration;
Youaskedforhelpabouthelpcategory:"Administration"
Formoreinformation,type'help<item>',where<item>isoneofthefollowing
topics:
BINLOG
CACHEINDEX
FLUSH
FLUSHQUERYCACHE
HELPCOMMAND
KILL
..........
--接下来，我们查看administration部分下的flush命令用法，直接输入helpflush;即可
mysql>helpflush;
Name:'FLUSH'
Description:
Syntax:
FLUSH[NO_WRITE_TO_BINLOG|LOCAL]
flush_option[,flush_option]...
TheFLUSHstatementhasseveralvariantformsthatclearorreload
variousinternalcaches,flushtables,oracquirelocks.Toexecute
FLUSH,youmusthavetheRELOADprivilege.Specificflushoptionsmight
requireadditionalprivileges,asdescribedlater.
--查看cacheindex的帮助信息
mysql>helpCACHEINDEX;
Name:'CACHEINDEX'
Description:
Syntax:
CACHEINDEX
tbl_index_list[,tbl_index_list]...
[PARTITION(partition_list|ALL)]
INkey_cache_name
tbl_index_list:
tbl_name[[INDEX|KEY](index_name[,index_name]...)]
partition_list:
partition_name[,partition_name][,...]
........................
--总结，即通过逐级help的方式即可获得与其主题相关的详细信息。--Author:Leshami--Blog:<atarget="_blank"href="http://blog.csdn.net/leshami">http://blog.csdn.net/leshami
</a>--比较常用的show命令，通常查看系统变量，状态变量等
mysql>helpshow;
Name:'SHOW'
Description:
SHOWhasmanyformsthatprovideinformationaboutdatabases,tables,
columns,orstatusinformationabouttheserver.Thissectiondescribes
thosefollowing:
SHOWAUTHORS
SHOW{BINARY|MASTER}LOGS
--设置系统变量，用set命令
mysql>helpset;
Name:'SET'
Description:
Syntax:
SETvariable_assignment[,variable_assignment]...
variable_assignment:
user_var_name=expr
|[GLOBAL|SESSION]system_var_name=expr
|[@@global.|@@session.|@@]system_var_name=expr
TheSETstatementassignsvaluestodifferenttypesofvariablesthat
affecttheoperationoftheserveroryourclient.Olderversionsof
MySQLemployedSETOPTION,butthissyntaxisdeprecatedinfavorof
SETwithoutOPTION.
URL:http://dev.mysql.com/doc/refman/5.5/en/set-statement.html