mysql common syntax functions
1. Generate random time
SELECT DATE_ADD('2021-01-01 00:00:00', INTERVAL FLOOR(1 + (RAND() * 10800)) SECOND )
Generate random numbers
SELECT UUID()
2. group by optimization
loose index Part of the scanned index needs to satisfy the left matching rule of the joint index. compact index Range index scan or full scan. There is a gap in ...
Posted by jmfillman on Thu, 19 Jan 2023 08:31:38 +0300
SQL statement exercises
1. Select all employees in department 30;
Note: All employees are to be checked
scoped to sector 30
code show as below:
mysql> select * from emp where deptno = 30;
2. List the names, numbers and department numbers of all clerks (CLERK);
Note: What you want to check is name, serial number and department serial number
clerk
code sh ...
Posted by TylerL on Thu, 05 Jan 2023 18:21:51 +0300
Database Study Notes
Database Study Notes (2)1. Database Security1.1 TCSEC/TDI security level classificationB1 level: "secure" or "trusted" products, truly secure products1.2 Database management system security control modelAccess control process:The database management system authenticates the database users who make SQL access requests to prev ...
Posted by speedyslow on Mon, 02 Jan 2023 10:48:29 +0300
Node.js in Action Chapter 3 What is a Node Web Program 3.3 Adding a Database
Node.js in action
Chapter 3 What is a Node Web Application
3.3 Add database
As far as adding a database to a Node program is concerned, there are no mandatory rules, but generally the following steps are involved.
Decide which database system you want to use.Check out popular modules on npm that implement database drivers or object-rela ...
Posted by garygay on Tue, 27 Dec 2022 03:38:58 +0300
Redis overview installation
# Redis overview installationApplication ScenarioCooperate with relational database for cacheVarious data structures store persistent dataRedis installationinstalled versioninstallation stepsBackground start (recommended)foreground startRedis introduces related knowledgeRedis is an open source key-value storage system.Similar to Memcached, it s ...
Posted by konrados on Sun, 25 Dec 2022 10:52:01 +0300
.net Revisiting the Past and Knowing the New: [10] CodeFirs, DBFirst for Getting Started with the .NET ORM Framework EFCore
Foreword: This series is about learning .net related knowledge by myself in order to keep up with the pace of .net cross-platform. The current working reason is basically below .net Framework4.7, so I have this series of learning summary, but it is not from The basic C# syntax and basic knowledge started, but around the important design and dif ...
Posted by Bah! Name on Thu, 22 Dec 2022 17:23:01 +0300
oss storage usage
Alibaba Cloud provides 5 ways to use oss storage, including console, command line, graphical management tool ossbrowser, SDK, and REST API; here are some descriptions of the commonly used command line and javasdk, and the others are not detailed one by one. Note, if you are interested, you can go to the official website to see related documents ...
Posted by newbie9999 on Wed, 14 Dec 2022 07:42:55 +0300
Mysql SQL optimization tracking to see how to optimize and decide which index to use or not to use
background
When using the index field to filter data, the explain query statement found that MySQL did not use the index, which raised doubts, so I decided to investigate why the index was not used, but the full table scan The result of the cause investigation is that when the amount of data you want to query is continuous and accounts for ...
Posted by Xonnie316 on Tue, 06 Dec 2022 11:57:13 +0300
Docker mongoDB container backup and recovery
Docker mongoDB container backup and recovery
word:
phonetic symbolstranslatedump[dʌmp]: [dang' mu' pu]dump; dump; dump; dumpdeny | denied[dɪˈnaɪ] :[di' nai]deny; deny; denydirectory[dəˈrektəri] :[di' ruai 'ke ' te 'rui]Table of contents
1. Data backup:
1. 1 Basic grammar:
>mongodump -h dbhost -d dbname -o dbdirectory
Example:
1. 2 ...
Posted by wmbetts on Tue, 06 Dec 2022 01:57:38 +0300
Detailed JDBC usage
Introduction to JDBC
Java Database Connectivity, (Java Database Connectivity, referred to as JDBC) is an application programming interface used in the Java language to regulate how client programs access the database, and provides methods such as querying and updating data in the database. JDBC is also a trademark of Sun Microsystems. We usua ...
Posted by naomi385 on Sun, 27 Nov 2022 20:52:51 +0300