Article directory The following two tables are explainedSELECTDISTINCTWHEREAND ORINBETWEENwildcardLIkeORDER BYfunctioncity tableString functionsCommonly used function examples:concatsubstrtrimregionreplacegroup byhaving Aliassubqueryexiststable linkUse subqueries to implement multi-table queriescreate viewunion intersection valueNo intersection valuecaseThe difference between null and no value (... »
Source code acquisition: Download from “Resources” on the blog homepage! 1. Project operationEnvironment configuration: Jdk1.8 + Tomcat8.5 + mysql + Eclispe (IntelliJ IDEA, Eclispe, MyEclispe, Sts support) Project technology: JSP + Servlert + html+ css + JavaScript + JQuery + Ajax, etc.; Personal Center Controller: /** * Personal Center Controller */ @Controller public cl... »
Source code acquisition: Download from “Resources” on the blog homepage! 1. Brief description of the project Function: User’s email registration, verification code verification and user login. There is no need to register an account, and you can also upload temporary files that meet the conditions, but they are only valid for 4 hours. File management, upload, download, rename, delete, ... »
📢📢📢📣📣📣 hello! Hello everyone,I am【Yixin classmate】, a highly motivated【Blogger in the Java field]!😜😜😜 ✨【Yixin classmate】ofwriting style: Like to use【Easy to understand] to explain every knowledge point, rather than using [large and luxurious] official statement. ✨【Yixin classmate】 Blogfieldyes【Back-end technology oriented], we will continue to update more [Backend technology】as well as【Learning e... »
Mysql basic knowledge If we want to understand mysql, let’s start with the most common process. If we enter a sql on the cilent side, what steps will we go through? Can think for 30s… A SQL query statement execution process select * from table where Id=4 To understand what this statement does, let’s first look at the entire architecture of mysql It is divided into client, server and storage ... »
1. Definition and function of check-inSigning in refers to signing or writing the word “arrive” on the prescribed book to indicate that one has arrived. Using this function in the APP can increase user stickiness and activity. An APP with a check-in function will often provide a sign-in replenishment function, and relevant rewards will be given for consecutive days of check-in; and in ... »
1. Background As the business continues to iterate, more SQL slow queries appear in the system. Although slow checking is not fatal, it will make merchants perceive that the system is slow and affect the user experience. We have accumulated some experience in the process of slow check optimization. Based on our practical experience, this article will explain the common causes of slow checking at w... »
Source code acquisition: Download from “Resources” on the blog homepage! 1. Brief description of the project The functions of this system include:Student management, teacher management, course management, grade management, system management, etc. 2. Project operation Environment configuration: Jdk1.8 + Tomcat8.5 + Mysql + HBuilderX (Webstorm also works) + Eclispe (IntelliJ IDEA, Eclisp... »
MySQL four attributes, isolation level The four major attributes of MySQL: A (atomicity), either all are completed or have no effect at all. The underlying implementation is implemented through undo log. When this transaction modifies the database, innodb generates the corresponding undo log. The undo log has multiple versions and stores the opposite operation to the previous version. It will reco... »
Source code acquisition: Download from “Resources” on the blog homepage! 1. Brief description of the project The functions of this system include: Super luxurious score management system, integration of three types of users: students, teachers, and administrators, curriculum management, score query, score details statistics, course entry, user management, and account management. 2. Pro... »
