Tag:Equivalence

  • Good luck! Cross blind box game you can’t miss at the beginning of the year

    Time:2021-11-17

    Hello, everyone. Today is the seventh day of the Lunar New Year and a good day for construction. So far, cross has 250000 user addresses. The development of cross, a decentralized NFT distribution and auction platform built with the support of cybervein foundation, is also ongoing. In the first quarter, in addition to opening b-end […]

  • Golang operator

    Time:2021-11-16

    operator The common operators in go language include arithmetic operator, assignment operator, relational operator, logical operator, etc Arithmetic operator operator describe Example result + Add 10 + 3 13 – subtract 10 – 3 7 * Multiply 10 * 3 30 / be divided by 10 / 3 3 % Surplus 10 % 3 1 […]

  • PHP ?? Convenient

    Time:2021-11-14

    $post = [ ‘page’ => 10, ‘b’ => 200 ]; $page = $post[‘page’] ?? 1; //Equivalent to $page = isset($post[‘page’]) ? $post[‘page’] :1; $page = $post[‘page’] ?: 1; //Equivalent to $page = $post[‘page’] ? $post[‘page’] :1; //This is the method of uploading files. False is returned if it fails $res = $this->uploadfile(); $img_path = $res […]

  • Some conclusions about locks in MySQL

    Time:2021-10-31

    summary Locks are usually used in computers to ensure data consistency when multiple processes or threads access the same data resource concurrently. MySQL is a very important part and is mainly used for concurrency control. In mysql, different locks are defined according to different dimensions (implementation mechanism, algorithm, compatibility and lock granularity). As shown below: […]

  • Thymeleaf

    Time:2021-10-20

    Spring integrates thymeleaf template engine, which is introduced in this article dialect Thymeleaf provides a flexible interface that allows users to customize their own dialects. Therefore, it is necessary to understand the standard dialect before customizing the dialect. Standard expression ${…}: variable expression Variable Variable expressions are usually ognl ${session.user.name} Thymeleaf <span th:text=”${book.author.name}”> Equivalent to […]

  • Big data development – detailed explanation of spark join principle

    Time:2021-10-13

    It is a common scenario for data analysis to join two data sets. In Spark’s physical planning stage, Spark’s join selection class will select the final join policy according to the join hints policy, the size of the join table, whether the join is equivalent or unequal, and whether the keys participating in the join […]

  • Talk about explain implementation plan

    Time:2021-10-11

    MySQL will select the most appropriate execution plan for all our query statements. This execution plan shows how to execute the query next. In our daily work, we can add the explain keyword in front of the SQL statement to view the specific execution plan. for instance: This is the most direct result we see […]

  • Data type conversion and operator

    Time:2021-9-26

    1、 Data type conversion Automatic conversionAutomatically promote small types to large types.byte -> short -> char-> int -> long-> float -> double int i = 1 ;byte b = 2 ;int j = b + i;Interpretation:If it is [byte x = B + I;], an error is reportedInt type (large) and byte (small) type operation, […]

  • Association table query method

    Time:2021-8-31

    preface Imagine the scene: Xiaobai is a newcomer to the workplace. When she sees a lot of database codes, she finds that she is not clear. Xiaobai cries anxiously and goes to Baidu in a hurry. She collects a lot of data and is very confused. It’s a mess Insect: for the convenience of little […]

  • MySQL practice notes (IV) practice (3)

    Time:2021-8-23

    10、 A statement that looks up only one line will also be slow Query does not return for a long time select * from t where id=1;Query results will not be returned for a long time. Generally, in this case, the probability is that the table t is locked. Next, when analyzing the reason, generally, […]

  • C language – distinguish the usage of typedef and #define, and understand the keyword typedef in one article

    Time:2021-8-10

    In C language, there is a typedef keyword, which is used to define user-defined types. Of course, we don’t really create a data type, but give existing or conforming and complex data types an alias that we can understand more easily. In short, we can use the typedef keyword to define our own type name. […]

  • Atomic operation & detailed description of sync / atomic package

    Time:2021-7-21

    package atomic import “sync/atomic” Atomic package provides the underlying atomic level memory operation, which is very useful for the implementation of synchronization algorithm. These functions must be used carefully. In addition to some special underlying applications, it is better to use the function / type of channel or sync package to achieve synchronization. Memory should […]