1. Basic knowledge
1.1 A procedure for data storage Storing data is the first step in processing data. Data can only be stored correctly for efficient processing and analysis. Otherwise, it can only be a mess, unable to start. So how can we store all kinds of business-related and complex data in an orderly and efficient way? In MySQL, a ...
Posted on Tue, 30 Nov 2021 22:35:36 -0500 by rsnell
Master the application of simple SQL query statements, including the application of conditions, like, top, order by, compute, etcMaster the application of connection query
1. Basic query
(1) Query all the information of all students in the Student table
select * from Student;
Posted on Tue, 30 Nov 2021 21:54:55 -0500 by servo
1. Insert Data
1.1 Mode 1: Add by VALUES
Case 1: Insert data in default order for all fields of a table
INSERT INTO Table Name
Each field in the table needs to be assigned a value in the value list, and the order of values must be the same as the order in which the fields in the data table are defined. ...
Posted on Tue, 30 Nov 2021 18:49:43 -0500 by essjay_d12
In actual development, we often encounter such situations: there are two or more interrelated tables, such as commodity information and inventory information stored in two different data tables respectively. When we add a new commodity record, in order to ensure the integrity of the data, we must add an inventory record to the invent ...
Posted on Tue, 30 Nov 2021 10:22:34 -0500 by matt86
1. Database object
2. View overview
2.1 why use views? On the one hand, views can help us use some tables instead of all tables. On the other hand, they can also make different query views for different users. For example, for a salesperson of a company, we only want to show him some data, but some special data, such as purchase p ...
Posted on Mon, 29 Nov 2021 07:41:45 -0500 by SnakeO
As a leading enterprise in the field of life services, Didi group is comprehensively testing and launching StarRocks. After more than a year of data system construction, we have gradually migrated some multidimensional data analysis requirements requiring real-time interactive query and ad hoc query from ClickHouse to StarRocks. StarRocks has a ...
Posted on Mon, 29 Nov 2021 05:44:53 -0500 by rokkstar
prefaceThis article will analyze how Mybatis parses the SQL statements in the mapping file and how each SQL statement is associated with the methods of the mapping interface during the loading of the configuration file. Before looking at the source code of this part, you need to have relevant knowledge of JDK dynamic agent. If you don't know mu ...
Posted on Sun, 28 Nov 2021 22:44:45 -0500 by rickmans
When s appears on the x permission of the file owner, it is called setupid bits or setupid. Its characteristics are as follows:
1.SUID permission is only valid for binary executables2. If the performer has x permission on the binary executable, the performer will have the permission of the owner of the file3. This permission is onl ...
Posted on Sun, 28 Nov 2021 12:42:58 -0500 by Catfish
Either all succeed or all fail
Transaction principle: ACID principle, atomicity, consistency, isolation, persistence (dirty read, phantom read...)
1. Basic concepts
Either all succeed or all fail
The data integrity before and after the transaction shall be consistent
Transaction isolation is ...
Posted on Sat, 27 Nov 2021 21:23:21 -0500 by Blissey
# database understanding
Database, container for storing data
Database management system, also known as database software or database products, is used to create or manage DB
Structured query language, the language used to communicate with the database, is not unique to a database software, but a common language for ...
Posted on Thu, 25 Nov 2021 13:15:57 -0500 by ataria