Description of requirements In the entity class AttributeVO, name and value have a one-to-one relationship. Only a certain status value is stored in the database and needs to be converted into corresponding text when returned to the front end. For example: is_deleted 1: deleted 0: not deleted confirm_status 1: Confirmed 0: Not confirmed -1: Not […]
Tag: relational
Java operators (arithmetic, relational, logical, conditional, assignment)
1 Operators in Java The symbols that operate on constants and variables are called operators, and the data involved in the operation are called operands. There are five types: arithmetic (special increment and decrement) operators, relational (comparison) operators, logical operators, conditional operators, and assignment operators. 1.1 Arithmetic operators Common ones are: + – * / […]
C++ Lesson 5 – Loops and Relational Expressions
For all source codes and exercises, please refer to github: https://github.com/fa-hui/cpp-primer-plus.git This chapter includes: for loop expressions and statements Increment and decrement operators: + + and – Combining assignment operators Compound statement (statement block) comma operator Relational operators: >, >=, = =, 0; If str1 comes after str2: strcmp(str1, str2) < 0; 5.2 Compare string-like […]
Springboot+Mybatis connects various relational databases and installs each database
Springboot + Mybatis connects various relational databases and installs each database Database download and installation For the download and installation of the database, it is recommended to download it from the official website and view the installation documentation on the official website. MySql download and installation Oracle download and installation SqlServer download and installation Springboot […]
CoreData/data storage management, CoreDataRelationships/relational data structure storage management usage
1. CoreData data addition, deletion, modification and query operations 1.1 Create data entity management file Click the menu bar File -> New -> File… -> Core Data, select Data Mode, and create the FruitsContainer.xcdatamodeld file. 1.2 Create FruitEntity entity table Open the FruitsContainer.xcdatamodeld file, click Add Entity, create the FruitEntity entity table, and add the […]
P31 C++ relational operator overloading, functors, C++ inheritance (unfinished)
Video address 6_bilibili_bilibili 1. Relational operator overloading == 》= != #include <iostream> using namespace std; class Box { public: Box(int a,int b) { this->a = a; this->b = b; } bool operator==(const Box & amp; another) { if( (another.a==this->a) & amp; & amp;(another.b==this->b)) { return true; } return false; } bool operator!=(const Box & amp; […]
Design of relational database tree structure
When designing programs, tree structures are often used to represent the relationships between certain data, such as upper- and lower-level departments of an enterprise, product classifications, file directories, etc. These tree structures need to be persisted with the help of a database, and relational databases do not have a corresponding native data structure to store […]
Operators: arithmetic operators, relational operators, logical operators, compound assignment operators, other operators
An operator is a symbol that tells the compiler to perform a specific mathematical or logical operation. C# has a rich set of built-in operators, classified as follows: arithmetic operators Relational operators Logical Operators compound assignment operator Bit operators Other operators Operator precedence (high to low) Category Operator Associativity Suffix ()[]->. + + — From […]
[Database System] Overview of query optimization methods in relational databases
Author: Zen and the Art of Computer Programming 1. Introduction 1. Definition “Database Query Optimization” refers to analyzing and processing the data or SQL statements entered by the user, extracting information from it and constructing a plan to execute the query, so that the entire process runs as efficiently as possible and the results are […]
Redis non-relational database configuration and optimization
Relational database and non-relational database Relational database A relational database is a structured database created on the basis of a relational model (two-dimensional tabular model) and is generally oriented towards records. SQL statements (Standard Data Query Language) are a language based on relational databases and are used to retrieve and operate data in relational databases. […]