to use if

Say 工欲善其事, its prerequisite. Today we will briefly introduce the next explain.Content navigation Id Select_type Table Type Possible_keys Key Key_len Ref Rows Extra Environment ready MySQL

The explain command is the first recommended command to address database performance, and most performance issues can be easily resolved with this command, explain can be used to see how SQL statements are executed, to help select better indexes and

I. GrammarExplain For example: Explain select * from T3 where id=3952602;Two. Explain output interpretation+----+-------------+-------+-------+-------------------+---------+---------+-------+------+-------+| ID | Select_type | Table | Type |

Java multithreaded--jdk and contract (2) thread poolAfter using the thread pool, the creation thread becomes the free thread from the line constructor, and the shutdown thread becomes a bad thread to the thread pool.The JDK has a executor framework,

In the advanced browser, we can bind an event when we know to bind an object, and then the handleevent method In this object will automatically enter the specified method, not to mention an example!!varEvents ={handleevent:function (Event) {

Personally think Ubantu under FCITX than Sogo useInstall FCITX first to Ubantu software center download FCITX Two software, one is the configuration software, one is the input method softwareKeyboard Input Method system is changed to FCITX in

Users want to use Ogg to synchronize data, the original use is Shareplex, as for why to change ogg,bulabula a bunch of reasons .... This is not what we want to care about, and the customer installed after the configuration of Ogg, the test, the

OSX uses the Unix file system, all the files are hanging under the directory "/" below, so there is no need to have the drive letter concept under Windows. For example, "C:" The hard disk you see on the desktop is hung under/volumes.For example, a

Mail alert mechanism in LinuxThe alarm mechanism in Linux is a key part of operation and maintenance management. We generally detect problems through monitoring, common monitoring software such as: Zabbix is now in use and ready to use. If we do

1.How to enter command line operation modeIn the graphical interface, open the Application utility terminal with the Finderor press F8 at boot, start with the-s parameter, and enter the command MOUNT-UW/Get permissionIn order to prevent misoperation

First, the basics of learning Shell scripts" Special symbols in theLinux shell "1. * : Represents 0 or more characters or numbers.Test can have no characters, or multiple characters, or it can be matched.2.? : represents only one arbitrary

How to learn a new programming language?The answer is: deliberate practice in the study area, 500 rows per day. What is the learning area, that is, you just have enough, but still need to pay a little effort.1. How to find a learning Area 1.1

PEP8 Specification Official Document: https://www.python.org/dev/peps/pep-0008/PEP8 Chinese Translation: http://www.cnblogs.com/ajianbeyourself/p/4377933.html the following from Https://www.douban.com/note/134971609/PEP8 Python Coding SpecificationA

Hibernate learning comes in mind:One: Hibernate's core classes and interfaces①configuration classThe use of it is: Read Hibernate.cfg.xml Managing Object Relational mapping Files Load Hibernate driver, URL, User: Managing

Final Final Variable (Before the keyword final is added to the defined variable, the variable is not changed once it is initialized.) The specific meaning of an immutable term is: Basic type whose value cannot be

PEP8 Specification Official Document: https://www.python.org/dev/peps/pep-0008/PEP8 Chinese Translation: http://www.cnblogs.com/ajianbeyourself/p/4377933.html the following from Https://www.douban.com/note/134971609/PEP8 Python Coding SpecificationA

The memory of the video card is divided into two parts, part is the video card comes with the memory called VRAM RAM, and the other part is the system main memory is called GTT RAM (the graphics translation table and the gart behind the same meaning,

a code Orchestration 1 indent. Indentation of 4 spaces (the editor can do this), no tap, no mix of taps and spaces. 2 The maximum length per line is 79, the line break can use backslashes, preferably with parentheses. The newline point is to hit

List of articles in this columnFirst, what is object-orientedSecond, C language can also achieve object-orientedThird, the non-elegant features in C + +Iv. solve the package and avoid the interfaceV. Rational use of templates to avoid code

ll (RPM) operating systems in Linux: Ubuntu9.04ll is not the next basic Linux command, it's actually LS-an alias for L. Ubuntu default does not support the command ll, must use LS-L, this is not very convenient to use. If you want to use this