• MySQL review 7: DDL add / delete / modify


    Continuous rain washed the scattered dust, by the way, also washed the leaves green. The rain will only be less and less, knowledge will be less and less. (within a certain range) Long query past, today will lead readers into the hall of DDL language, feel the unique SQL statement! #DML language Data manipulation language […]

  • How do I reduce the number of lock locks to the minimum in parallel programming step by step to achieve lock free programming


    In parallel programming, we often encounter the problem of shared sets of operations among multiple threads. It is very difficult for us to avoid this problem and achieve a state of lock free programming. You also know that once the shared set is locked, the concurrency and scalability ability will often have a great impact. […]

  • Static page


    1、 Introduction to static web page 1. Overview It is to change a dynamic page (. PHP) into a static page (. HTML), and subsequent users can directly access the static page. Page static technology is divided into two types: true static and pseudo static. True static: turn a dynamic page into a static page, […]

  • Datatable common functions


    The new DT is obtained by conditional query and sorting string clumname = “”; string filtcontext = “”; string wherecode = clumname + “='” + filtcontext + “‘”; /// <summary> ///The new DT is obtained by conditional query and sorting /// </summary> ///< param name = “DT” > source DT < / param > ///< […]

  • MySQL big table pagination (with unique secret technique)


      Background of the problem The order table in MySQL (InnoDB) needs to be paged and queried in chronological order, and the primary key is not incremental in time dimension. The order table is more than one million in size. How to effectively realize this requirement? Note: This article does not mainly explain how to […]

  • SQL associated query


    Extract the associated data from two or more tables There are several types of associated queries: Inner join: inner join, cross join (1) Form 1 Select field list From a table inner join b table On Association condition [where other screening criteria] Note: if do not write association conditions, there will be a phenomenon: Cartesian […]

  • SQL case statements and decode functions


    Database table: select * from rec order by rst,game_time; ID GAME_TIME RST 2 January – January – 11 F 6 January – January – 11 F 3 February – January – 11 F 9 February – January – 11 F 7 March – January – 11 F 1 January – January – 11 W 4 […]

  • Javase Part 04: the loop structure of java basic syntax


    This article will explain in detail the loop structure and random object in java basic syntax, and will have different exercises, especially loops, which are almost everywhere in software development. Chapter 1: circulation structure 1.1 – why learn cycle structure (understand) For example, the existing requirement: in the command window, output 100 lines of “Hello […]

  • Advanced operation of mongodb query (multi condition query, regular match query, etc.)


    Advanced operation of mongodb query Introduction to grammar Mongodb queries documents using the find() method, while the find() method displays all the documents found in an unstructured way. –1. Basic grammar db.collection.find (query, projection) — returns all documents that meet the query criteria db.collection.findOne (query, projection) — returns the first document that meets the query […]

  • JavaScript basics-03


    1. Conditional judgment statement If the condition is not true, the condition will not be executed; ifsentence Grammar 1:     if(conditional expression)       {sentence}          :trueJust execute,falsenon-attachment that ‘s ok; Grammar 2:     if(conditional expression)       {sentence}        else  {sentence} Grammar 3:      if(conditional expression)       {sentence}        else  if (conditional expression){sentence}     else  if (conditional expression){sentence}     else{sentence} 2. Conditional branch statement:switchsentence Grammar: […]

  • Linux system programming — conditional variable


    Condition variables are used to wait for threads rather than locks. Condition variables are usually used with mutexes. The reason why condition variables are used together with mutexes is that they have only two states: locked and non locked. Condition variables can make up for the insufficiency of mutexes by allowing threads to block and […]

  • https://juejin.im/post/5d750947f265da03ea5aa2a2


    Recently, there is a requirement to switch positions after dragging the ItemView of the list. After searching the Internet, we found that recyclerview is easy to implement this scheme. The default API of recyclerview is very powerful, and it only needs a few lines of code to realize simple drag and drop requirements. There is […]