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summary This article mainly uses the Navicat for MySQL tool to analyze the common constraints of the SQL language through programming and code testing: primary key constraints   And foreign key constraints. Each table in the business needs to have one and only one primary key. There can be multiple foreign keys in a table, but ...

1, Ajax (1) Introduction to Ajax          1. Introduction to Ajax          Ajax is a web development technology to create interactive web applications. Is a technology for creating fast dynamic web pages.          Ajax is ...

1: Background 1. Tell a story A few days ago, when debugging a bug on the IOT cabinet terminal, I found that the database connection string in app.config is encrypted. To switch the database during debugging, I need to decrypt the ciphertext on a special gadget. After changing the database name on the connection string, I have to encrypt and ...

1, Short answer 1. Briefly describe the MySQL version used by your company, and specify the specific minor version and GA time? 5.6.38 5.7.20 2017-9-13 2. Please introduce the type of database you are familiar with and the representative product name? NoSQL:Redis Mongodb memcache RDBMS:Oracle MySQL MSSQL PG 3. Please briefly describ ...

Data definition The main function of DDL is to define database objects (such as database, data table, view, index, etc.). DATABASE (DATABASE) --Create database CREATE DATABASE test; --Delete database DROP DATABASE test; --Select database USE test; Data TABLE (TABLE) --Create data table --Normal creation CREATE TABLE user ( id int(10) ...

Addition, deletion and modification of data processing 1, Insert data 1.1 practical problems Solution: use the INSERT statement to INSERT data into the table. 1.2 mode 1: add VALUES Using this syntax, only one piece of data can be inserted into the table at a time. Case 1: insert data in the default order for all fields of the table ...

Download and configuration tutorial of MySQL installation free version There is a previous version of this blog. If readers are still interested in the author's previous version of the blog, you can visit this link: https://blog.csdn.net/wangpaiblog/article/details/111938395 [description] This tutorial describes the download and conf ...

Master slave replication working principle Master slave replication is a high availability and high performance solution provided by MySQL. The working principle is divided into the following three steps: 1. The master records the data changes in * * binlog * *. 2. The I/O thread from the slave saves the binary log read from the master lib ...

Do the last task, create a new file, put in the QR code and output: First, let's talk about how to make java generate QR codes. There are actually many open source tools here. I recommend using Zxing. First, let's explain how to use Zxing: First visit https://github.com/zxing , and download: After downloading, unzip it, as shown in the fo ...

insert data         Single tuple insertion insert into Student(Sno,Sname) Values ('95020','Chen Dong')         Insert subquery results Insert into Deptage(Sdept,Avgage) select Sdept,AVG(Sage) from Student Group by Sdept Modify data         update...set...where update Sutdent set Sage ...