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 ...
Posted by rgilchrist on Sun, 28 Nov 2021 11:11:26 -0800
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 ...
Posted by porta325 on Sun, 28 Nov 2021 00:33:27 -0800
1, Short answer
1. Briefly describe the MySQL version used by your company, and specify the specific minor version and GA time?
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 ...
Posted by peppeto on Sat, 27 Nov 2021 23:23:41 -0800
The main function of DDL is to define database objects (such as database, data table, view, index, etc.).
CREATE DATABASE test;
DROP DATABASE test;
Data TABLE (TABLE)
--Create data table
CREATE TABLE user (
id int(10) ...
Posted by little_tris on Fri, 26 Nov 2021 19:46:31 -0800
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
Posted by phpdev12 on Fri, 26 Nov 2021 18:12:50 -0800
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
This tutorial describes the download and conf ...
Posted by infratl on Fri, 26 Nov 2021 14:56:22 -0800
Master slave replication
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 ...
Posted by jay_bo on Fri, 26 Nov 2021 12:30:43 -0800
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 ...
Posted by robertaccettura on Fri, 26 Nov 2021 09:38:14 -0800
Single tuple insertion
insert into Student(Sno,Sname) Values ('95020','Chen Dong')
Insert subquery results
Insert into Deptage(Sdept,Avgage)
Group by Sdept
update Sutdent set Sage ...
Posted by novice4eva on Fri, 26 Nov 2021 09:22:56 -0800