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brief introduction In the previous article, we found a critical path code for converting logical SQL to real SQL. In this article, we will explore some details of statement parsing generation based on the previous article Source code analysis The code generated by the key parsing of the statement is as follows: @RequiredArgsConstructor publ ...

1, View (keyword: view) 1. View creation -- Basic format for creating views: create view <View name> as <Query statement>; -- The essence of view is to use<View name>replace<Query statement>，This is equivalent to aliasing the query statement. select * from class; create view v_c as select * from class; -- Created a ...

How to calculate user retention problems with sql 1, Retained 1. Meaning of retention: Retained: refers to the number of users who arrive at the APP on the base date and return to the APP on the next n days; Retention rate = number of users returned on the day n days after the base date / number of users on the base date * 100% Or refers t ...

Summary This article is a relatively low and simple point of knowledge 1, Delayed Loading (Lazy Loading) Postpone loading until data usage;Only when accessing methods such as ToList/ToArray/First/FirstOrDefault(), delayed loading of navigation properties, etc.Only load data Example of delayed loading of navigation attributes using a proxy a ...

1,hibernate.cfg.xml Comment out this section of configuration <!--Update database level automatically--> <!--<property name="hbm2ddl.auto">create</property>--> 2. New Generate Database Table Tool Class public class HibernateSchemaExport { static Session session; static Configuration ...

1. Background Because the business of the project is constantly moving forward, it is unavoidable that the number of tables in the database will become larger and larger, constantly squeezing hard disk space.Business growth cannot be sustained even with the greatest amount of space, so it is necessary to regularly delete unnecessary data.A tab ...

There is a deep doubt about laravel-admin's picture upload mechanism. Deleting avatar pictures on the user information page will cause an error. It was 1.4 at that time, and later updated 1.5 found that the delete button disappeared directly. If you use image normally in the form during the process of use, the slight ...

When I do the project again, the customer needs me to implement a function, probably when adding classifications, if the database has the same classifications, the jsp interface will prompt for information and cannot be added successfully.The results are as follows:   Below is the idea for implementation: 1. First implement an onblur event in ...

1. Scenarios for use In general, there are test environments and formal environments for our development.Of course, databases are also separate.If you could use phpmyadmin to directly access mysql on both servers.This is the need. 2. Solutions 1. Find under the phpmyadmin folderConfig.sample.inc.php, renamedConfig.inc.php. 2. OpenConfig. ...

It is relatively simple for Linux to back up the database regularly. crontab can be used for scheduled backup. If windows is used, it may be troublesome. 1.Linux: Step 1: configure the backup directory code on the server: mkdir /var/lib/mysqlbackup cd /var/lib/mysqlbackup Step 2: write backup script code: vi dbbackup.shPaste the f ...