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Author: Song Shaohua 1, Reading guide Optimization is very important to improve the performance of the database itself in the case of hardware and non system failures. Each type of database has its own different ways to track and optimize the database. These methods include not only the optimization of the parameters of the database system it ...

5. Connection query Sometimes, you need to use a SELECT statement to query data in multiple tables. For this purpose, you can use join queries. Connection query is divided into inner connection, outer connection, cross connection and self connection. Inner connection and outer connection are common connections; The result of cross connection i ...

Many injections have no echo, which may be caused by the problem of SQL query method. At this time, we need to use relevant error reporting or blind injection for subsequent operations. sql statement addition, deletion, modification and query: For example, insert statement injection can be used to inject into the database during user reg ...

WAF bypass - SQL injection Conduct operations on data, such as case, encryption and decryption, encoding and decoding, so as to make the interception invalid For example, take sqlilabs-less-2 as an example (assuming that the security dog has been set to prohibit querying the database): At this point, when you enter the following statement ...

MySql 1) Data Definition Language (**DDL * *) such as database and table building 2) Data Manipulation Language(**DML * *), such as adding, deleting and modifying records in a table 3) Data Query Language(**DQL * *), such as query operations in tables 4) Data Control Language(**DCL * *), such as setting user permissions   Addition, delet ...

preface This paper briefly summarizes the data query statements and reviews what I wrote when reading Basic grammar Single line note:-- Multiline comment / **/ 1, Single table query 1. Select several columns in the table --Query specified column select sno, sname from student; --Query all columns select * from student; --Query ...

1, Experimental purpose Master the basic syntax of SELECT statement and the expression method of query conditions;Master query condition expression and usage;Master the function and usage of GROUP BY clause;Master the function and usage of HAVING clause;Master the function and usage of ORDER BY clause. 2, Experimental class hours 2 class hou ...

Injection principle Boolean blind annotation is applicable when there is no echo during injection. The principle is that the application system makes Boolean judgment when querying according to the where+and statement, that is, the result is true or false, for example, select * from admin where id=1 and 1=1. In general, the application sys ...

sql classification DDL (data definition language) database definition language Some sql used when creating table views, such as CREATE, ALTER, DROP, etc. DDL is mainly used to define or modify database, table and view structures DML (data manipulation language): These are the SELECT, UPDATE, INSERT and DELETE that we most often use. It is mainl ...

The Database in MySQL is like a container, which contains various objects. For example, data tables, views, stored procedures, and triggers. Among them, the Table is the main object for storing data. The relationship between them is shown in the figure below:This chapter mainly introduces the creation, viewing, selection and deletion of databas ...