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Histogram, a special type of statistical information of columns, can provide more detailed data distribution information of columns in the table. Histogram stores values in buckets. Based on the number of different values and the distribution of data, the database selects the type of histogram to be created. The types of histogram are as follow ...

0. Preface The previous four articles introduced an excellent framework SqlSugar developed by domestic developers, which gave us a bright feeling in front of our eyes. In this article, we will try another ORM framework, Dapper, which has a relatively high audience rating. Dapper is a lightweight ORM framework, which is characterized by high spe ...

In the process of warehousing and logistics, it is often necessary to use thermal printer or carbon tape printer to print some barcode and information and paste them on the physical object or package The best way is not to directly use thermal code to form text and output it to printer for printing But thermal code is also a special language to ...

This article will use a simple login comment function to fully introduce the use of mybatis framework. Functions: add, delete, modify, query, multi table query, fuzzy query, dynamic query This article uses the environment / tools: Database: mysql 5.7 JDK:8 IDEA:2020.1 Database visualization tool: Navica ...

This paper reviews the knowledge of database, including creating database, creating table, primary key constraint, foreign key constraint and table relation (many to many). 1, Table description A user table, a role table, and a permission table. A user corresponds to multiple roles, a role corresponds to multiple ...

PHP encryption function - md5() function encryption instance usage MD5() function is the MD5 hash value of calculator string. Using MD5 algorithm, the full name of MD5 is message digest algorithm 5. Its function is to calculate data information of different length into a 128 bit value through a series of algorithms, that is, to change a byte st ...

overview There are two very famous improvements in java8, one is Lambda expression and the other is Stream. Stream is a stream. Its main function is to search and filter Collection data. It is similar to SQL database operation. The difference between stream and Collection is that Collection is only responsible for storing data, not for other ...

view Meaning: Understand as a virtual table and use it like a regular table A new feature of MySQL version 5.1 is data generated dynamically from tables For example: a comparison between a dance class and an ordinary class Differences between views and tables: Name Create Grammar Keyword Use Occupy physical space view ...

Preface Recently, we are trying to use a log system, graylog, to collect the slow query log of mysql for subsequent analysis, monitoring and alarm. The test steps have been completed and the logs have been collected successfully. During the test, you need to brush some slow query logs. In order to brush more logs and not have a greater impact o ...

There are some serious bug s in the code written before to realize simple network communication. Write in detail later. According to the last code, mainly increased the user registration, login page, and realized the real-time display of the current login status of the number of people. And solve some bug s not found last time. (refer to previo ...