[summary] if the server where CentOS is located is limited to security reasons and the customer does not configure us to access the Internet, how to install the PostgreSQL database? This article will explain in detail how to install PostgreSQL12 database offline on CentOS7 system through specific steps.
1 offline installation package preparati ...
Posted by rathlon on Wed, 01 Dec 2021 00:41:39 -0800
1, Annotation development
1.1 comparison between annotations and xml
xml: as a configuration file
Advantages: it can extract content (decoupling), clear configuration, convenient positioning and easy to findDisadvantages: complicated configuration
Note: xml development can be replaced
Advantages: fast development speed and no cumbersom ...
We can divide the functional architecture of Mybatis into three layers:
API interface layer: interface APIs provided for external use. Developers use these local APIs to manipulate the database. As soon as the interface layer receives the call request, it will call the data processing layer to complete the specific da ...
Posted by killfall on Tue, 30 Nov 2021 07:38:13 -0800
mybatis supports different databases. The specific access to the database is the driver jar package provided by different database manufacturers. For example: mysql-connector-java.jar of MySQL
The jar s provided by different manufacturers are also implemented based on the interface in the java.sql package under the JDK For example, different d ...
Posted by pulkit123 on Tue, 30 Nov 2021 00:31:47 -0800
2, Mycat global serial number
Mycat can guarantee id uniqueness in the following ways:
1) Local file mode
2) Database mode
3) Timestamp mode
4) ZKID generator
5) ZK increment ID
4 and 5 are recommended
In the above 5 methods, the global serial number configuration should be enabled in the server.xml file and the autoIncrement attribute of the l ...
Posted by AlanG on Mon, 29 Nov 2021 19:27:34 -0800
Django's operation on the database (addition, deletion, modification and query)
1. Add data
>>>from entry name.models import Table name to import
>>>Variable name = In which table do you want to add the name of the data table(
Added data,for example:name = 'Xiao Ming',
age = '18'
Posted by lukeurtnowski on Mon, 29 Nov 2021 12:33:51 -0800
MySQL Learning Notes
Log on and exit MySQL server
# Log in to MySQL
$ mysql -u root -p12345612
# Exit MySQL database server
-- Show all databases
-- Create a database
CREATE DATABASE test;
-- Switch database
-- Show all tables in the database
-- Create Data Table
CREATE TABLE ...
Posted by DotSPF on Mon, 29 Nov 2021 10:42:45 -0800
1, Importance of data backup
In a production environment, data security is critical Any loss of data can have serious consequences Causes of data loss Program error Human operation error Operation error disk failure Disasters (e.g. fire, earthquake) and theft
2, From a physical and logical point of view, backup can be divided into
Posted by patrickm on Mon, 29 Nov 2021 10:19:24 -0800
Answer #11: what is the difference between char and varchar in MySQL
1. Experimental scenario
GreatSQL 8.0.25 InnoDB
2. Experimental test
parametercharvarcharIs the length variableFixed lengthLengthenstorage capacity 0 ~ 2550 ~ 65,535
2.2 construction test table
CREATE TABLE vc (v VARCHAR(4), c CHAR(4));
2.3 test without ...
Posted by terje-s on Mon, 29 Nov 2021 07:43:18 -0800
Mybatis inserts multiple records using the @ Insert annotation
Several methods of converting JSONObject to List
In a large software engineering job, if an administrator wants to send messages to multiple users, the front end needs to send an array with user numbers to the back end. Here is a summary of several methods for the back-end to rece ...
Posted by mzfp2 on Mon, 29 Nov 2021 07:27:19 -0800