Programmer Think

catalogue 1, Why do I need multi table query? 🐟 Which city does an employee named "Abel" work in? 2, How to implement multi table query 1. Error of Cartesian product (cross connection) ① Wrong implementation ② Cause of error The query method of the table requires multiple conditions ① Join condition of two tables ② If a fiel ...

I am a graduate of 21 years with one year's work experience. My resume and professional skills are as follows. Now I review and prepare for the interview according to my resume and knowledge. Record date: January 15, 2022 Most knowledge points are only briefly introduced, and the specific contents are reviewed in detail according to the re ...

1. Succession 1.1 implementation of inheritance 1. Concept of succession Inheritance is one of the three characteristics of object-oriented. It can make subclasses have the properties and methods of the parent class, redefine them in subclasses, and add properties and methods 2. Format of implementing inheritance Inheritance is impleme ...

1, Why addressing We know that data is stored in memory. The CPU needs to use the data stored in memory. To use a data, we need to find the data in memory. What to find is to use the memory number, that is, the address, to find the location of the data in memory, take it out for use, or put it back to the specified locationThe above is an addr ...

I choice question 1. [C language] read the program and select the result (D) int main() { int a = 5; if( a = 0 ){ printf("%d", a - 10); } else { printf("%d", a++); } return 0; } A. -5      B. 6      C. 1      D. 0 Parsing: note that the if statement if (a = 0) is an equal sign, which is an assignment at this ti ...

Guide: many friends analyze data for two minutes and run for two hours? In the process of using SQL, we should not only pay attention to the data results, but also pay attention to the execution efficiency of SQL statements. This article involves three parts with a long length. It is suggested to read it after collection: SQL introductio ...

Say something before brushing If you want to cut the length of the article, you will say it in addition to the length of the code, Because too much time is wasted in writing articles! In fact, it's not difficult to brush the questions. What's difficult is to insist! This column is the classic title of sword finger offer, And record you ...

catalogue 1, Overview of collections: 1. Differences between sets and arrays: 2. Features of the collection: 2, Collection interface: 1. Various functions in Collection: 2, Traversal of collection: 1. Use the acquisition function to realize traversal: 3, List interface (inherited from Collection interface) 1. Features of List interface ...

Members of the HandlerMapping family can be divided into two branches. One is inherited from AbastractUrlHandlerMapping, the other is inherited from AbastracHandlerMethodMapping, and both are inherited from AbastractHandlerMapping. The green box AbstractHandlerMapping abstract class implements the skeleton logic of [obtain the processors and ...

Python wechat ordering applet course video https://edu.csdn.net/course/detail/36074 Python actual combat quantitative transaction financial management system https://edu.csdn.net/course/detail/35475 How to input the adjacency matrix stored on disk into R program is the starting point of social network analysis. The basic data structure and c ...