SQL injection concept
Basic concepts of database
Data refers to the symbols that record and identify objective events. It is the physical symbols or a combination of these physical symbols that record the nature, state and relationship of objective things. It is a recognizable and abstract symbol.
See for details Baidu ...
Posted by carleyvibe on Thu, 11 Nov 2021 00:10:37 -0800
After the database is built, we can then create tables that actually store data. When creating a table, you first need to describe what the table looks like, what columns it has, what types of data these columns are used to store, etc. this description of the table is called the structure or definition of the table. With the structure of the ta ...
Posted by madmega on Wed, 10 Nov 2021 16:34:38 -0800
This article is reproduced from the official account of "good future technology". The use of Flink CDC 2 is introduced in the case of Flink SQL, and the core design of CDC is interpreted. The main contents are as follows:caseCore designCode explanationGitHub address https://github.com/apache/flinkWelcome to like Flink and send star~In ...
Posted by murdocsvan on Wed, 10 Nov 2021 15:35:58 -0800
When the client connects to the MySQL server, it must provide valid identity authentication, such as user name and password. When the user performs any database operation, the server will verify whether the user has corresponding permissions. For example, SELECT permission is required for query tables and DROP permission is required for deletin ...
Posted by dreamer on Wed, 10 Nov 2021 12:52:00 -0800
In mysql, a set of tables is called a database. The MySQL server manages several databases. There can be several tables under each database. Draw a diagram as follows:
When we just installed MySQL, many databases and tables were built in it. We can use the following command to see which databases are available:
Posted by vasse on Wed, 10 Nov 2021 09:52:42 -0800
DB: databaseDBMS: Database Management SystemSQL: Structured Query Languagedatabasedata sheetfield
After mysql is successfully installed, common commands:
mysql [-h host ip -p port] - u user name - p enter enter password to log inshwo databases; Display all databases after successful loginuse database name; Open data ...
Posted by richo89 on Wed, 10 Nov 2021 00:30:09 -0800
DB:DataBase (database, which actually exists as a file on the hard disk) DBMS: DataBase Management System MySQL Oracle SQL: structured query language, is a standard general language. When the SQL statement is executed, it will actually be compiled internally before executing the SQL. DBMS is responsible for executing SQL stateme ...
Posted by ulrikqk on Mon, 08 Nov 2021 14:17:59 -0800
Classification of SQL
classificationexplainData definition languageFor short, DDL(Data De "nition Language) is used to define database objects: database, table, column, etc.Data manipulation languageReferred to as DML (data management language), it is used to update the records of tables in the database.Data query languageDQL(Data Query L ...
Posted by rhock_95 on Mon, 08 Nov 2021 13:28:40 -0800
create table test01 (
a1 int(4) not NULL,
a2 int(4) not NULL,
a3 int(4) not NULL,
a4 int(4) not NULL
alter table test01 add index idx_a1_a2_a3_a4(a1,a2,a3,a4);
explain select a1,a2,a3,a4 from test01 where a1=1 and a2=2 and a3=3 and a4=4; -- Recommended writing
explain select a1,a2,a3,a4 from test01 where a4= ...
Posted by chris9902 on Mon, 08 Nov 2021 12:47:05 -0800