• Winfrom paging with gridcontrol and DataNavigator in devexpress


    1. Pagination requires an SQL program to write down. First, I will provide the idea of SQL. For pagination SQL, I have introduced it in my previous post, but I will not introduce it one by one Select top PageSize * — display quantity from (select row_number() Over (order by eg [ID ASC) as rownumber, […]

  • History recording mechanism in Bash


    Basic Usage Show history UsehistoryYou can view the latest execution of the current userHISTSIZEThese records are stored inHISTFILEIn file, inbashIt is automatically loaded into the history buffer queue at startup, and its simple use method is as follows: >History displays all history 1 ip a 2 exit 3 ls -la 4 history >History 2 displays […]

  • View MySQL execution plan


    1. MySQL syntax MySQL provides the explain syntax for query analysis. Add an “explain” before the SQL statement. By default, MySQL profiling is turned off, so you must first turn on profiling set profiling=”ON” mysql> show variables like “%profi%”; +————————+——-+ | Variable_name | Value | +————————+——-+ | profiling | ON | Show processlist; view the […]

  • Detailed explanation of total record optimization of count query in paging component


    1 background When using the paging function of mybatis plus (hereinafter referred to as MBP). We found a paging optimization class of jsqlparsercountoptimize. The official didn’t give a detailed introduction to it. We didn’t find any words to analyze this kind of logic on the Internet, which we dare not use. It’s also convenient for […]

  • How to query the result by another time field in the case of grouping?


    If there is such a table: The script is as follows: DROP TABLE IF EXISTS `jl_site_operation`;CREATE TABLE `jl_site_operation` ( `id` int(11) NOT NULL AUTO_INCREMENT,`Site [ID ` int (11) default null comment ‘station ID’,`Param_id ` int (11) default null comment ‘parameter ID (associated jl_parameter_config table ID)’,`Param_value ` varchar (255) default null comment ‘the value corresponding to […]

  • Mongodb update operation


    update operation Update fields across databases Getsiblingdb get other databases db.getCollection(‘xxx’).find({“field_name”:{“$lt”:20000000}}).forEach(function(_item){ db.getSiblingDB(“other_db”).collection_name.update({“feild_name1”:_item.field_name1},{$set:{“field_name2”:_item.field_name2}},false,true); }) Getsiblingdb (“other? DB”) specifies the database to span Getsiblingdb (“other? DB”). Collection? Name specifies the table name collection? Name Update the fields in the array $elemMatchMatch the data in the data$setTo update db.getCollection(‘xxx’).update({ “name”:”bc2c2e9676e74600274d3e3738bab5c6a27dc85d560563b695fece08b6a7f7de”, “array_name”:{“$elemMatch”:{“type”:”control”}}, }, {“$set”:{“array_name.$.amount”:15000000}} ) Update field name DB. […]

  • Do you think that blockchain looks like the 200 yuan I borrowed from you?


    In recent days, blockchain has appeared again, and the news media have been reporting a lot, claiming that it may set off a wave in the financial sector. Some even say that mahjong, the product of blockchain, appeared in China a long time ago. So what is the blockchain and what is the relationship between […]

  • The implementation of verification code and QR code login under. Net core


    In the previous article, the implementation of access control layer under. Net core mainly introduces the realization of logical level permission control through middleware. This article mainly introduces how to generate verification code and two-dimensional code under. Net core. Generate verification code The logic of the verification code is relatively simple. It generates a random […]

  • SAP SD free goods


    SAP SD free goods   In some industries, such as retail, chemical industry and consumer goods industry, discounts are usually offered in the form of free goods.   Free items can be a part of the order quantity, not included in the invoice, which is called include bonus quantity; both the order and free items […]

  • Database version management: flyway exploration and Practice


    Introduction:If you are an independent developer or do not need to maintain multiple systems, maintaining the database version is not complicated. But if your team is rapidly iterating or developing multiple functions at the same time, deploying your services on multiple production servers in parallel in multiple environment versions, database management will become a hassle. […]

  • [mongodb] mongodb paging display


    Pagination with mongodb limit and skip methodMongodb limit() methodIf you need to read a specified number of data records in mongodb, you can use mongodb’s limit method. The limit () method accepts a number parameter, which specifies the number of records read from mongodb.Mongodb skip() methodIn addition to using the limit () method to read […]

  • Simple C ා log class


    In a recent C project, you need to print logs and organize a tool class. The code is as follows: public class Logger { private static readonly Logger Logg = new Logger(); private string _className; private Logger() { } public static Logger GetLogger(string className) { Logg._className = className; return Logg; } public void WriteLogs(string dirName, […]