Programming VIP

Chapter 7 single line function 1. Understanding of function 1.1 what is a function Function runs through the use of computer language. What is the role of function? It can encapsulate the code we often use and call it directly when necessary. This not only improves the code efficiency, but also improves the maintainability. In SQL, we can al ...

In the process of developing program system, we often need to consider the problem of system security, Like this, it's like your database is running naked, isn't it? Maybe someone quietly deleted the database and let you run away? Therefore, the plaintext password cannot appear in the configuration file. Next, I will give you a detailed in ...

Greenplum 6.17 cluster construction 1, Cluster planning Hostipfunctionmaster192.168.2.20mastersegment1192.168.2.21segmentsegment2192.168.2.22segment The password is 1 2, Environmental description nameexplainoperating systemCentos7Database installation packageopen-source-greenplum-db-6.17.2-rhel7-x86_64.rpm 3, Preparation before installation ...

prefaceAfter reading the title, will you be surprised how Kunlun distributed database plays a distributed file system?Since version 0.9 of Kunlun distributed database requires the addition of HDFS distributed file backup function, my little brother will share the learning process in his work.HDFS (Hadoop distributed file system) is the core sub ...

FastAPI day 4 1. Multi application management When we develop, a large number of routes are often involved. If all routes are written in one file, it is not conducive to us to modify a route and its processing function, and it is not conducive to the later maintenance and upgrading of the whole project. Moreover, the number of code lines ...

MySQL -- index creation principle 1. Data preparation Create database and table create database if not exists testindexdb; use testindexdb; create table student_info( id int(11) not null auto_increment, student_id int(11) not null , name varchar(20) default null, course_id int not null , class_id int(11) defaul ...

prefaceThe previous article introduced the scenario of index invalidation( Talk about the failure of MySQL index ), the explain execution plan is used. The execution plan returns the information of each step in the execution process instead of executing it.Through the returned one or more rows of information, each part of the execution plan and ...

Experimental questions Basic Operation of Experiment 3 Database (1) Create a database textbook: CREATE database textbook (2) Display and modify the maximum number of connections show variables like "max_connections"; set global max connections = 8; (3) Delete the database textbook drop database textbook Experiment 4 Definition and Mo ...

(1) Clone the table and generate the data records of the data table into a new table 1. Method 1: use like create table test1 like info; #Using the LIKE method, copy the KY08 table structure to generate the test01 table insert into test1 select * from info; 2. Method 2: direct cloning CREATE TABLE test2 (SELECT * from info); show cre ...

reference material https://www.bilibili.com/video/BV1Kr4y1i7ru?p=32&spm_id_from=pageDriver 1. Constraints 1.1 general Concept: constraints are rules that act on fields in a table and are used to limit the data stored in the table.Objective: to ensure the correctness, validity and integrity of the data in the database.classification ...