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At present, the database is divided into: Relational database:             mysql，sqlserver，Oracle Note: the data is stored in the data table, which is stored in the computer disk Non relational database:             mongoDB，redis Note: the data is stored in the computer memory, so it is faster to read and write data To insta ...

When initializing DM database, there is a parameter LENGTH_IN_CHAR feels difficult to understand, so refer to the official documents and Study on the online blog First look at the official documents for length_ IN_ Interpretation of char parameters Whether the length of an object of type VARCHAR is in characters. Values: 1, Y means yes, 0, N m ...

1. Overview of new MySQL8 features 1.1 MySQL8.0 New Features 1. Simpler NoSQL support NoSQL refers generally to non-relational databases and data storage. With the rapid development of Internet platform, traditional relational databases have become increasingly unsatisfactory. MySQL has been supporting simple NoSQL storage since version 5.6. ...

Optimization of a query You should encounter this scenario. A self incrementing primary key is set in MySQL, but some data is subsequently deleted, resulting in discontinuous primary keys. You can use the following command to query those discontinuous primary keys. -- Writing method 1 select id from (select id from Table name order by id asc ...

4, DDL (data definition language) 4.1 data type 4.1.1 numerical type type typeTINYINTSMALLINTMEDIUMINTINT/INTEGERBIGINTbyte12348 characteristic Both unsigned and signed can be set. They are signed by default, and unsigned can be set through unsigned.If it exceeds the range, an out or range exception will be reported, and the critical v ...

A good memory is better than a bad pen. If you can write down something, you can write it down. If you have time to take it out and have a look, you will find a different feeling. catalogue preface Zero, class diagram and flow chart 1, Main process 1: get connection process 2, Main process 2: initializing pool objects 3, Process 1.1: obta ...

Dual machine hot standby scheme Kept + MySQL master-slave replication to realize active and standby 1.1 deployment mode The two servers deploy the same running environment and services. The running environment includes java running environment, redis, mysql, kept and java background services 1.2 realization effect When the background process of ...

background The user needs to perform ocr identification. In order to prevent the interface from being brushed, there is a limit (the number of calls per minute cannot exceed xxx). After investigation, we decided to use the incr and expire of redis to implement this function Note: the following code is implemented using golang First edi ...

Note: this blog is MySql table operation instruction 1. If you want to learn the basic MySql instructions, you can use the author Blog Learning; If you want to practice further, you can do it after learning Operation 2 After that, according to Blog MySql instance Practice! Add, delete, query and modify ~ simple instructions Create table ...

This article is mainly aimed at the addition, deletion, modification and query of MySQL and upgrading again. If you want to see the basic additions, deletions and changes, you can see the previous article of the blogger. Here, the blogger posts a link for you: https://blog.csdn.net/weixin_53033446/article/details/119005596?spm=1001.2014.3001.55 ...