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Talking about database transactions, talking about databases I. SQL transactions 1. What is a transaction: a transaction is an inseparable logical unit of work. It is used as the smallest control unit to execute concurrent operations on the database system. All the database operation commands contained in the database are submitted or withdrawn to the system as a whole. These database operation commands are

Talking about the stored procedure in the database and talking about the stored procedure in the database I. Differences between stored procedures and functions: 1. In general, the functions implemented by stored procedures must be more complex, while the functions implemented by functions are more targeted. 2. For stored procedures, parameters (output) can be returned, while functions can only return value

Talking about PHP weak type security, talking about php0x00 weak type No one doubts the simplicity and power of php. It provides many features for developers, one of which is the weak type mechanism. You can perform such operations in a weak type mechanism. Php does not strictly check the input variable type, or can convert the variable type freely. For example, in the comparison of $ a = $ B $ A = null

Talking about several methods of external storage allocation, talking about external storage allocation External Storage refers to memory other than cpu cache and memory. Hard disks, optical disks, and USB flash disks can all be called external storage. All the data also exists here, so the allocation method becomes extremely important, which directly affects the computer's running speed. External Storage a

Talking about MySQL temporary table and derived table, talking about mysql Derivation About derived tables When the primary query contains a derived table, or when the select statement contains the union clause, or when the select statement contains the order by clause of a field (group by clause of another field, in order to complete the query, MySQL needs to automatically create a temporary table to store

Talking about Mysql specified ordered query, talking about mysql ordered Query Recently, I made a big screen presentation project, similar to displaying shift information at airports and railway stations. However, the presentation content is much more complicated. Some of the data is as follows: The front-end mainly uses the Vue framework and requires that the back-end data be displayed on the front-end, F

Talking about SpringMVC internationalization support, talking about springmvc Internationalization This week, the company's leadership hoped that I would work out an international solution for a project, study for two hours, and adopt SpringMVC's international support. Principle: Register localeResolver (Regional parser) in DispatchServlet and add Locale Interceptor (LocaleChangeInterceptor) to detect chang

Talking about JVM and memory allocation, talking about JVM Memory Allocation 1. program memory allocation Initial Memory Allocation When a program is ready to run, it first needs memory from the Java virtual machine, but the Java Virtual Machine itself does not have the permission. It can only apply for memory from the operating system. At this time, the Java Virtual Machine will have an initial memory, He

Talking about the problem of mysql password forgetting and logon error, talking about the problem of mysql password forgetting The mysql logon password is forgotten. In fact, the solution is simple. You only need to add a line of "Skip authorization table" parameter selection in the mysql main configuration file my. cnf! Add the following line to my. cnf: [Root @ test-huanqiu ~] # Vim/etc/my. cnf // Add it

Talking about memory leakage caused by js closures, and talking about js In the js closure, you can define "local variables", but if you call them externally, especially when you call values repeatedly, it will cause a large amount of memory overhead. How can this problem be prevented? There are no similar memory or efficiency issues with closures. Do you need to pay attention to them? How to avoid it? Me

Talking about the operations of the Python set type -- Parallel delivery, talking about python Reading directory • Introduction• Basic operations• Function operations Introduction Python's set is an unordered, non-repeating element set. Its basic functions include link testing and elimination of repeated elements. The set object also supports addition, intersection, difference, and symmetry difference. Sets

Talking about data parsing in Python, talking about python Parsing Import OS; -- Python built-inPrint (OS. getcwd () -- get the current working directoryOS. chdir ('/Users/longlong/documents') -- convert to the/Users/longlong/Documents directory.OS. path. join (parm1, parm2,...) -- constructs a path name from one or more path fragments.OS. path. expanduser () -- used to include ~ The path of the symbol is e

Talking about the relationship between servlet and jsp, talking about servletjsp Servlet is written in java and a java class. The main function is to accept and process client requests, and return the processing results to the client for display. Jsp is a product of the later development of servlet. Before jsp is available, servlet uses the output stream to dynamically generate the entire HTML page. The out

Talking about how to implement two file replication methods in Python, and talking about how to implement two methods in python The example in this article mainly implements the file copy operation in Python. There are two methods. The specific implementation code is as follows: # Coding: UTF-8 # Method 1: Simulate file copying using read () and write () # create a file hello.txt src = file ("hello.txt",

Talking about the capturing group and non-capturing group in PHP regular expressions, talking about the php capturing Group Today, I encountered a regular expression matching problem and suddenly turned to the concept of a capturing group. The manual was a little over, baidu has no intention of turning to the special usage of Regular Expression capturing groups in C # And Java. When the search keyword is PH

Talking about PHP's solution for high-traffic flash sales and talking about php flash sales A Real-time countdown display of hours, minutes, And seconds is required. The modification date and time on the user side does not affect the normal display of the Countdown (that is, the server time prevails ). In fact, this is the same as the Time Limit Function of many examination systems. You cannot use ajax to r

Talking about php string reverse interviews, talking about strings 1. single-byte string Inversion Php provides the strrev () function for string inversion () $ Str = 'abcdef'; echo strrev ($ str ); 2. mb_substr () is required for multi-byte strings that contain Chinese characters () $ Str = 'string'; function rev ($ str, $ encoding = 'utf-8') {$ len = mb_strlen ($ str); $ result = ''; for ($ I = $ len

Talking about how to implement the Hook mechanism in PHP, talking about the phphook Mechanism I am not familiar with the concept of "Hook". Recently I saw a php framework using this mechanism to expand projects. So I 'd like to know about it. The so-called Hook mechanism is a popular technology in Windows programming. The main idea is to bury (preset) a hook in advance where functions may be added. This hoo

Talking about the use and principle of Yii optimistic lock, talking about yii This article introduces the use and principles of Yii optimistic locks. I will take a study note and share it with you. I hope it will be useful to you. Principle: The data table uses an int type field to store the version number, that is, the version number recorded in this row. When updating data, compare whether the version num

Talking about JS inheritance _ borrow constructor combined inheritance, talking about js borrow Constructor 2. Borrow Constructors To solve the problem of containing reference type values in the prototype, we use a technology called constructor stealing (also known as forged objects or classic inheritance ). The basic idea of this technology is to call a super-Type constructor within a subclass constructor