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the where clause having . You can use exist and not exist instead of In and not. You can use table links instead of exist. Having can be replaced by where , if not replaced, can be handled in two steps. Example SELECT * from ORDERS WHERE customer_name not in (SELECT customer_name from CUSTOMER) Optimized SELECT * from ORDERS WHERE customer_name not exist (SELECT customer_name from CUSTOMER) 7.2 do not declare numbers in character format, you want to declare character values in numeri

database version select version ();• View database status show status;(data not all shown)• View each parameter show variables; Show variables like ' max_connect% ';Show variables;(Too many parameters)• Modify parameter set global max_connect_errors=1000;If you want to permanently take effect, you need to exit to SHELL,VIM/ETC/MY.CNF, define max_connect_errors=1000;• View queue show processlist; Show full processlist;If there are errors, please correct, learn from each other and progress togeth

rows affected (0.01 sec)• Completely delete the database:Drop database db1;mysql> drop Database db1; Query OK, 1 row affected (0.01 sec) 13.6 MySQL Database backup recovery• Backup library:Mysqldump-u User name-p password Database > backup data file path[Email protected] ~]# mysqldump-uroot-p123456 mysql >/tmp/mysql.sql(Too much data is not listed)• Recovery library:Mysql-u User name-p password Database [Email protected] ~]# mysql-uroot-p123456 MYSQL2 • Backup table:Mysqldump-u Use

the WHERE clause is used in the inch , not in , or or having . can use exist and the Not exist Replace inch and the not in . You can use table links instead exist . Having can be replaced by where , if not replaced, can be handled in two steps. ExampleSELECT * from ORDERS WHERE customer_name not in(SELECT customer_name from CUSTOMER)Optimized SELECT * from ORDERS WHERE customer_name not exist(SELECT customer_name from CUSTOMER)7.2 do not declare numbers in character format, you want to dec

10.28 Rsync Tools IntroductionThe file Synchronization tool rsync, can achieve incremental copy, CP is direct coverage, low efficiency;Install rsync, #yum-y install rsync;Rsync Common methods,Copy the passwd file to the/tmp directory, rename it to 1.txt, and the command to #rsync-av/etc/passwd/tmp/1.txt-V visualization;Remote copy, command for #rsync-av/etc/passwd [email protected]:/tmp/1.txt; then enter the password;10.29/10.30 rsync Common Options10.31 rsync sync via ssh-e Specifies the port,

14 weeks four sessions (May 14)16.1 Tomcat Introduction16.2 Installing the JDK16.3 Installing Tomcat16.1 Tomcat Introduction16.2 Installing the JDKOpen the download URL.Click jdk=8u144-linux-x64.tar.gz, downloadUpload to LinuxCtrl+f Open XftpPut the downloaded file in the root directoryXftp is an SSH-based port that does not require FTP to be opened.CopyAt the bottom, pasteCheck to see if the installation is successful, the following results appear, stating that there is no problem, the command

();-------------------------------------------------------------------curl-x127.0.0.1:80 test.com/upload/3.php //Can not parse, directly to the source code (written content) display/usr/local/nginx/sbin/nginx-t/usr/local/nginx/sbin/nginx-s Reloadcurl-x127.0.0.1:80 test.com/upload/3.php //Normal parsingTail/usr/local/nginx/logs/error.log//View error log12.16 Nginx AgentCd/usr/local/nginx/conf/vhostVim proxy.conf//Add the following:-----------------------------------------------------------------

Tags: Linux notes12 weeks three sessions (April 25)12.10 Nginx Access Log12.11 Nginx Log Cutting12.12 static files do not log logs and expire time12.10 Nginx Access LogThe format of the configuration file is in the main configuration file.Search for log to find the following paragraph, which is used to define the format.Public network IP, in Baidu, search IP, view.Defining Access Log pathsOpen FileUnder}, add a row to read as follows:12.11 Nginx Log CuttingEdit FileAdd the following contentProce

= ' date-d '-1 day +%y%m%d '//similar to 20180427, yesterday's date, today 28thLogdir= "/data/logs"Nginx_pid= "/usr/local/nginx/logs/nginx.pid"CD $logdirFor log in ' ls *.log 'DoMV $log $log-$dDone/bin/kill-hup ' Cat $nginx _pid '--------------------------------------------------------------------------------------Add Task Schedule #crontab-e//write the following:0 0 * * */bin/bash/usr/local/sbin/nginx_logrotate.sh//Daily 0 o'clock in the morning execution12.12 static files do not log logs and e

The title of the following ten articles was originally "10 lessons for young designers", which is John C Jay's ten lessons for young designers, but it is helpful to all normal young people, it has nothing to do with the designer profession, so I expanded the scope of the title without authorization and translated it in a bit. Ten lessons learned for young peopl

Java predecessors: Learning the experience and lessons learned from the EE process I'm here to talk about My Learning the Java EE process and the lessons learned in this process. So that later people less detours.Java development to now, according to the application to divide into three major chunks: J2se,j2me and Java EE. These three blocks complement each other and are used in different ranges.J2SE is the

Review the mistakes made by zcom over the past year and share some of the lessons of last year. The biggest mistake is losing focus . We did a lot of acquisitions last year, we made a lot of investments and even invested in an in-house media company. The mode of their magazine is to put a magazine rack in the hotel room, and put their own and outside magazines to sell ads. They want to replicate Jiangnan spring's niche pattern, where we felt there was

than the code generated by the lock--try/finally--unlock idiom required by lock. The code is read much more often than it was written. When programming, communicating with others is much more important than communicating with a computer, so the readability of the code is critical. Therefore, it is meaningful to start with the Synchronized keyword and only replace it with the lock object when performance tuning is done. 21.9.2 Lock-free container

How to solve the grub error during startup-pain lessons-general Linux technology-Linux technology and application information. The following is a detailed description. If you have installed more than two systems (I am talking about Ubuntu), Grub will be used for guidance. I have tried this situation, when xp and ubuntu are started, grub loading please wait appears during startup ...... Error 17 or error 15 I have never seen such a situation before. W

During happy pregnancy, the APP has been unavailable for a few months, but there are still four to five users each day. Although the project failed, but in general, it is more successful than the previous debate project. Now let's summarize: Experience: 1. The product orientation must be urgent and helpful to users to solve users' actual problems. (Solve actual problems during pregnancy, and there are still users visiting each day) 2. products must meet users' psychological needs. (Through th

The following are some of the lessons I've been inspired by the software development process over the years, as well as the good experiences that have been summed up.Development starts from the trivial and then expandsWhether it's creating a new system or adding new functionality to an existing system, I always start with a version that's simple enough to have almost no functionality, and then fix the problem step-by-step until you're satisfied. I hav

Because they have just graduated into society, a lot of things do not understand, the lack of human life, the future is also more confused, so in the online search of some predecessors summed up the experience and lessons, so that they can in the future combined with their own actual situation to go a few detours, I hope to everyone useful.1, the first three years of work, do not care so much about the treatment, even in the case of no impact on life,

unspoken intention is to do so. The result is that the next day to study the problem, the solution is ready to go.21. Job-HoppingDon't be afraid to switch jobs. It is very interesting to work with different people, to develop different products and to feel different company culture.22. Continuous LearningWe need to constantly learn and understand software development. You can try different programming languages and tools, read the software development books, and accept the MOOC course. Believe

Testing to do is confused, is to do a balm, or drift, I do not know, but I know that-I want to do a good test, can affect more people's testing. Perhaps because of a variety of reasons, do not feel the value of testing, but want to make their own value, first let yourself worth, and then you are worth the value of the show you.How far can you go without a coded test? So programming is bound to be, no matter when, perhaps a bit extreme, but I am the position of the individual is this. (not arguin

3. Lessons learned from more than 2 million yuan of entrepreneurship-apps are not needed for entrepreneurship, but more than million apps Abstract: There is an idea to develop apps or websites, promote, continuously improve, and explore profit models. This general mobile Internet entrepreneurial process. However, I think that in some specific business models, the "R D app or website" step can be cut down or postponed. Health care sharing: Part