Database: primary key
Database ☞ primary key This paper is mainly based on the corresponding learning of the database, and summarizes an important knowledge point in the database - primary key! Some other knowledge points, such as foreign key, relational database, etc., will be interspersed in the middle. preface ThUTF-8...
Posted by smokebusted on Thu, 13 May 2021 07:29:44 +0930
Pitfalls and suggestions in table design
1. Number type 1.1 integer type Is the quantity field signed or not? Generally speaking, the quantity can not be negative. It is reasonable to use unsigned. But the following situation, do this kind of subtraction statistics, then the error will come. The calculated value is negative, out of thUTF-8...
Posted by websmoken on Sat, 15 May 2021 02:54:35 +0930
MySQL Learning Notes
MySQL Learning Notes SQL: Structure Quevy Language 1. Basic Knowledge DDL: Data Definition Language DML: Data Operating Language - Operating Records in Database Tables DQL: Data Query Language DCL: Data Control Language - Define access and security levels 1. Login Method mysql -uroot -p123456 -UTF-8...
Posted by psy on Sun, 16 May 2021 02:35:33 +0930
Single column split multi column query and combined display of Mysql written examination questions
Single column split multi column query and combined display of Mysql written examination questions The thing is this: one day in the development group to see peers chatting, a peer sent a mysql written test. I studied for several hours with a try mentality. Don't talk too much, go straight to tUTF-8...
Posted by comicrage on Sun, 16 May 2021 07:54:56 +0930
[Brush Java Foundation + sql once a day] 2021-5-18
Preface Yesterday, I took a written test for a company and felt that my basic knowledge was weak, so I plan to brush some java basic knowledge questions to improve my proficiency in basic knowledge.However, the efficiency of not reviewing or correcting my own errors is also very low, so I intenUTF-8...
Posted by smudge on Wed, 19 May 2021 01:50:04 +0930
Unique Clothing Library-Sales Clothing-Analysis Case Actual Warfare (BI-SQL-Python-Excel)
The main difference between this article and the web is that data analysis is done separately (using BI) (using MYSQL) (using Python) (using Excel). 1. BI (Visual Display (PC and Mobile) The following four diagrams are pieced together, and the data can be linked (filter criteria, different compUTF-8...
Posted by dml on Thu, 20 May 2021 05:26:00 +0930
Review Mysql
Review Mysql emp table +-------+--------+-----------+------+------------+---------+---------+--------+ | EMPNO | ENAME | JOB | MGR | HIREDATE | SAL | COMM | DEPTNO | +-------+--------+-----------+------+------------+---------+---------+--------+ | 7369 | SMITH | CLERK | 7902 | 1980-12-17 | 800.UTF-8...
Posted by cshinteractive on Sat, 22 May 2021 03:24:05 +0930
A brief review of Mysql
A brief review of Mysql affair A complete business logic unit is indivisible Transaction-related statements Only DML statement (insert delete update) transactions exist to ensure data integrity and security Only one DML statement does not require a transaction mechanism 3.5. About isolation betUTF-8...
Posted by Ali_baba on Sun, 23 May 2021 01:55:40 +0930
Centos7 installs the MySQL8 database (no pits!!!)
1. System Environment Information 1.1 Query System Version cat /etc/redhat-release cat /proc/version The CentOS version of the current installation environment is 7.9, and the system is 64 operating systems for the Linux 3.10 kernel. 1.2 Clean up installed packages 1. yum update #upgrade yum (UTF-8...
Posted by fallenangel1983 on Sat, 29 May 2021 01:35:17 +0930
Using MySql hot standby function in Linux system
summary Purpose of the experiment Verify and test the hot standby function of MySQL under Linux system. Test environment Prepare two servers, install the operating system and database respectively, and the database version should be the same. Environmental projectsEnvironment configurationremaUTF-8...
Posted by shonuff on Fri, 04 Jun 2021 08:50:43 +0930