Summarized from database principle and application (MySQL Edition) Tsinghua University Press
#In syntax,  indicates that this part is optional, < > indicates that this part is required, and is not written when writing specific commands, # as a single line comment, / * * / multiple lines
1, Data definition
1. Create database
Posted on Sat, 09 Oct 2021 06:00:12 -0400 by pastcow
testrecord database stores player behavior records, which need to be cleaned up every three months.
Preparation before deleting data
To view the size of the testrecord database:
MySQL [(none)]> USE information_schema;
MySQL [information_schema]> SELECT CONCAT(ROUND(SUM(DATA_LENGTH/1024/1024/1024),2),'GB')
-> a ...
Posted on Thu, 07 Oct 2021 17:15:58 -0400 by shortysbest
MyBatis is a very popular ORM framework at present. Its function is very powerful, but its implementation is relatively simple and elegant. This paper mainly describes the architecture design idea of MyBatis, discusses several core components of MyBatis, and then explores the implementation of MyBatis by combining a select quer ...
Posted on Thu, 07 Oct 2021 02:14:27 -0400 by everogrin
Hello, I'm spicy.
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Database advanced fe ...
Posted on Thu, 07 Oct 2021 00:04:36 -0400 by DESIGNGRAPHY
All database learning summary articles are summarized according to the shangsilicon Valley video of station B, and the video links are as follows:
Data definition language is mainly used for Library and table management. CREATE keyword: CREATE Modify keyword: ALTER Delete keyword: DROP
Posted on Wed, 06 Oct 2021 22:27:06 -0400 by miniu
data typeDQL languageDML languageDDL languageDCL languageTCL languageNon foreign key constraintForeign key constraintForeign key policyDDL and DML add a littleMulti table query syntaxSubqueryaffairTransaction concurrency problemTransaction isolation levelView + stored procedureJDBC+sql injection + other
Installation: uninstall all mysql and ma ...
Posted on Wed, 06 Oct 2021 17:13:50 -0400 by le007
In the previous chapters, I only learned about the principles of using indexes and what indexes to use with the explain keyword. The next two chapters consider how to make better use of indexes.
drop table `employees`;
CREATE TABLE `employees` (
`id` int(11) NOT NULL AUTO_INCREMENT,
`name` varchar(24) NOT NULL ...
Posted on Mon, 04 Oct 2021 20:44:10 -0400 by alco19357
I. MyBatis Loading Policy
1. What is delayed loading?
Problem: Configuration and implementation of one-to-one, one-to-many, many-to-many relationships in Mybatis is achievable Object's associated query. Many times in the actual development process we don't always need to load user information before we have to load his order information. This ...
Posted on Mon, 04 Oct 2021 12:32:20 -0400 by cayman_d