• Transaction isolation level


    Transaction isolation level What is a business? A transaction is a logical set of operations, either executed or not executed. The most classic example of transaction is transfer. If Xiaoming wants to transfer 1000 yuan to Xiaohong, the transfer will involve two key operations: reducing the balance of Xiaoming by 1000 yuan and increasing the […]

  • C # to convert TXT document to table


    C # implementation of TXT document conversion code: public DataTable TXTToDataTable(string fileName, string columnName) { DataTable dt = new DataTable(); FileStream fs = new FileStream(fileName, System.IO.FileMode.Open, System.IO.FileAccess.Read); StreamReader sr = new StreamReader(fs, System.Text.Encoding.Default); //Record one line of records read at a time string strLine = “”; //Record the contents of each field in each line […]

  • Analysis of hive modeling


    Modeling analysis The discussion is based on the case of visitor system Purpose of modeling analysis Analyze which levels, tables and fields the whole data warehouse needs ODS layer: source data layer Docking source data, keep the same granularity as the source data DWD Task: 1. Cleaning. Incomplete data Expired or invalid data 2. Conversion […]

  • What does go ORM do?


    Fat Sir: next, I’ll give you a pie Chief: come on!!A note from ORM What is ORM? Why ⽤ ORM? What is ORM, or object relational mapping? Its purpose is to make a mapping between relational databases and objects, In this way, we don’t need to deal with complex SQL statements when we operate the […]

  • An update statement from a colleague made me miserable enough


    Source: ju.outofmemory.cn/entry/336774 Recently, several development students have asked me on the nail, such as the following figure: The problem can be summed up as follows:Update a record in MySQL. The syntax is correct, but the record has not been updated When I first encountered this problem, I got this statement and executed it directly in […]

  • Zipper table of data warehouse


    Zipper WatchIt is defined according to the way of table storing data in data warehouse design. As the name suggests, the so-called zipper is to record history.Record all the changes of a thing from the beginning to the current state. The following is a zipper table, which stores the most basic information of users and […]

  • Front end training intermediate stage (51) – nodejs operation mongodb, document curd operation


    The most basic of the front end isHTML+CSS+Javascript. If you master these three technologies, you can get started, but you are only getting started. Now the definition of front-end development is far more than that. Front end classroom(HTML/CSS/JS)In order to improve the level of technology and lay a solid foundation of knowledge, we have a […]

  • Several forms of GIT merge


    The three operations of GIT merge are: [merge], [squash merge], [rebase merge] background In master_ 0 trunk pull up a branch branch_ 0, at brandch_ I submitted a comment 3 times on 0. 1. merge Use the command: $ git checkout master_0 $ git merge brantch_0 Submit history at this time:This is brantch_ All submission […]

  • The three major MySQL logs that must be understood – binlog, redo log and undo log


    Source:https://juejin.im/post/686025…Author: get up at half past six The log is mysql As an important part of database, it records all kinds of state information during database operation. mysql Logs mainly include error log, query log, slow query log, transaction log and binary log. As development, we need to focus on the binary log( binlog )And […]

  • MySQL index optimization strategy (all)


    The so-called index is to sort some specific algorithms for specific MySQL fields, such as binary tree algorithm and hash algorithm. Hash algorithm is to establish eigenvalues, and then quickly search according to the eigenvalues. The binary tree algorithm BTREE is the most used and the default of MySQL. For the fields indexed by BTREE […]

  • What are the configurations for adding insert element tags in mybatis configuration file?


    How to add insert element label Adding records does not return the primary key configuration Add record to return primary key 1 (property configuration) Add record to return primary key 2 (property configuration) Batch add record return affects the total number of record rows (property configuration) Case practice Adding records does not return the primary […]

  • InnoDB lock mechanism — checking a slow insert query


    In the slow query log, an insert statement is issued, and the probability of slow query is relatively high. A simple insert takes 4-10s, which is very unusual. Insert statement is attached and some fields are omitted INSERT INTO `fc_pay_out_trade_log` (`out_trade_no`,`dateline`) VALUES (‘191120093724940457’,1574185044) [ RunTime:4.176669s ] fc_ pay_ out_ trade_ Log table except primary key, […]