A lot of friends in the tuning with MySQL will certainly use the explain to see the execution of the SELECT statement, here is a brief introduction to the results of the meaning of the two columns.1 Type column The official saying that this column represents the "type of access", and more commonly, the way MySQL finds the data rows needed. One is to introduce the worst from the most efficient to the best: all this is called a full-table scan, and no i
Meaning of DBUnitdb, or decibel, is a very common unit in the field of electronics. This unit is characterized by the use of logarithms to represent the original data. 1 shell = 10 db = 10dB = 10 times times PowerFor an amplifier,power Magnification Ap = ten lg (PO/PI)voltage Magnification Au = LG (UO/UI)current Magnification Ai = LG (IO/II)For example: amplifier magnification of 40dB, indicating that its voltage amplification is 100 times times, curr
Option meaning of info. plist, meaning of info. plist
1. application does not run in background (container name: UIApplicationExistsOnSuspend) from the end of iOS4.0, when you apply the program line, press Home terminal, the application does not parse the current line, but hides in the background. Therefore, if you want to download the current program line after you press Home then, check this option.
2. A
This may be used in the shell, including DOS.Null is something called a null bucket, and the benefit of redirecting the output to it is that the file size is not constantly increasing due to too much content in the output. In fact, you think that null is nothing, that is, the output of the command is discarded.1 indicates standard output, 2 indicates standard error output, 2>1 indicates the standard error output is redirected to standard output, so that the normal output and error output of the
The meaning of the forest root domain in the domain tree, and the meaning of the domain forest root domain
Contoso has many IT resources in the company's IT environment, and these IT resources are all in a state of decentralized management, which virtually increases the management cost of contoso, moreover, the management system cannot be implemented in the actual production environment.
So how can we solv
[Go] Return html tags for their original meaning, and html tags for their meaning
To tell the truth, the word "div + css" does not know how many people are harmed. Maybe the author's intention is correct, but the followers have misinterpreted its meaning in terms of performance, the whole page should be a combination of div + css files. In this way, there is no v
The recent use of curl feeling is still very convenient, looked at the cookie file format of curl generated, some of the value of the meaning is not very clear, to find some information about the cookie looked down, do a memo The cookie file format generated by PHP Curl is as follows #Netscape HTTP Cookie File#http://curl.haxx.se/rfc/cookie_spec.html#This file is generated by libcurl! Edit at your own risk.Jifen. xx.comFALSE/FALSE0PHPSESSID Dmdvk314ru
Chapter eighth Introduction to object-oriented programmingThe contents of this chapter:What is object-oriented programmingOOP technologyThe Windows forms application's dependency on OOP8.1 Meaning of object-oriented programmingThe programming method described earlier, called function (or procedural) programming, often leads to so-called single applications, where all functions are contained in several code modules (often a code module). with OOP, many
Android Log Tag meaning, androidlogtag meaning
One of the most important methods to analyze Android problems is to analyze logs in events. there are many system logs in the log, some of which are not very familiar with the meaning. The following is the system log tag obtained from the android source code.
The Tag description is as follows: "30005 am_create_activi
Where T: class meaning, whereclass meaning
public class DbEntityEntry
This is a parameter type constraint. The specified T must be of the Class type.
. NET supports the following types of parameter constraints:Where T: struct | T must be a structure typeWhere T: class | T must be of the Class typeWhere T: new () | T must have a non-argument ConstructorWhere T: NameOfBaseClass | T must inherit the class nam
Linux basic [Folder meaning], linux basic meaning
The linux File directory is a tree directory.
Bin --> Executable File
Boot --> operating system boot file, system kernel, boot Information
Dev --> device, device information, computer hardware device information
Etc --> System Configuration directory
Home --> home Directory, user folder
Root --> super administrator folder with the highest Permissions
Python: The Meaning of self and __init__ + why have self and __init__ backgroundsReply:I wrote some python tutorials that need to be able to seeQuestions from Songshoujiong:What is the meaning of self,__init__ in python?Why do you have to have self,__init these things?Before you explain, let's say a few words.1. So far, although I have written not very little Python code, but there is really not too much co
We all know that Chinese characters are hieroglyphs, but if English is also hieroglyphics, you will think pure nonsense. In fact, the origins of the 26 letters of English do come from hieroglyphs. The 26 letters originally originated from Egyptian hieroglyphics, and the Phoenician alphabet was later modified by the Phoenicians, and the Greeks reformed the Phoenician alphabet to create the Greek alphabet, in which the ancient Romans reformed the Greek alphabet and invented the Latin alphabet, whi
The meaning of life, a very large and broad question, there is no definite answer. Everyone has a different view and understanding, 1000 readers there are 1000 of Hamlet. When you see this book, you must also be thinking about what is the meaning of life, how to live out the meaning of life."Life is meaningless, but you have to define a
After reading the book, "living out the meaning of life," a lot of feeling, "what is the meaning of life?" "This is a very hard question to answer. Many of the sentences in the book are thought provoking, prompting me to think about my life and my own meaning.The author of "Living out the meaning of life" is the famous psychologist Frankel. He was a marvel of the
CharactersMeaning: For a character, it is usually expressed as literal meaning that the next character is a special character and is not interpreted.For example:/b/matches the character ' B ', by adding a backslash in front of B, which is/b/, the character becomes a special character, indicatingMatch the dividing line of a word.Or:For several characters, the usual description is special, which indicates that the characters immediately followed are not
Reference
In the C ++ programming language 3rd (Bjarne stroustrup, 1997:Page 1:Objects of some user-defined types contain type information.SuchObjects can be used conveniently and safely in contexts in which theirType cannot be deter-mined at compile time.
In the previous article, "fan Feng ignition: Also on the meaning of Bjarne stroustrup" Object-based ", and B4 master"ArticleI don't think its logic is very clear, because the specific
how do you differentiate between sending and receiving? By default, the DCE sends data to the DTE, and when DTE decides to send data to DCE, the RTS is valid, indicating that the DTE expects to be sent to the DCE, and that the DCE cannot immediately convert the send and receive status, and DTE can determine if the CTS is valid to see if it can be sent. This avoids the loss of data caused by the DTE being sent when the DCE is not ready. Full double working hours, these two signals have been vali
, no basketball awareness, no team sense, I played the position is the defender, and this person really difficult to cooperate, and with the team members of the same without teamwork consciousness, which once made me very tangled , the result is that I am floating in an outside line, become a useless person. And then this guy can not see the past, said I do not play, people are lazy, Daladala, well, I did not explain, I admit very lazy, for a programmer, let's say that is his praise to me.By thi
The meaning and relationship of nal, slice and frame in H.NAL Nal_unit_type 1 (encoding strip for non-IDR images), 2 (coded stripe data split block a), 3 (coded stripe data split block B), 4 (coded stripe data block C), 5 (encoded stripe of IDR image) typesAndThree coding modes for slice species: I_slice, P_slice, B_sliceThere are 3 types of frame: what is the mapping between I-frame, P-frame, and B-frame?Finally, what frame does the 6 (SEI), 7 (SPS),
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