Programmer Think

catalogue 1.C3P0 Preparation before use: Method 1: hard coding (database configuration is written into the code) Method 2: write configuration file and separate code and configuration (development recommendation) 2.DBCP Preparation before use: Method 1: hard coding (database configuration is written into the code) Method 2: write config ...

PYTHON reptile diary 01 Record your learning reptile diary Choose python as the programming language 1. Environmental preparation python3.6+ mysql pycharm 2. Ideas The goal is to climb the top 100 of the cat's eye ​ 1. Analyze the law of url ​ https://maoyan.com/board/4?offset=10 Find their URLs and use the url parameter offset as th ...

Realization motivation The simplification and integration of configuration are the two main problems that line expressions want to solve. In the cumbersome data fragmentation rule configuration, with the increase of data nodes, a large number of repeated configurations make the configuration itself difficult to maintain. The line expression c ...

catalogue 1, First knowledge database 1.1 types of DBMS 1.2 common system structure of RDBMS 1.3 database installation 1.3.1 introduction to Alibaba cloud MySQL server 1.3.2 introduction to building local MySQL environment 2, First knowledge of SQL 2.1 concept introduction 2.2 basic writing rules of SQL 2.3 creation of database (CREATE DATABASE ...

Chapter 56 SQL function $EXTRACT A string function that extracts characters from a string by position. outline $EXTRACT(string[,from[,to]]) parameter String - the target string from which to extract the substring.from - optional - the position of a single character in the target string, or the beginning of the range of characters to e ...

Fuzzy Query Using like is called a fuzzy query and is also a type of conditional query that supports% or underscore matching: (% is a special symbol, _is also a special symbol) %: match any number of characters _: Any character. For example: Find names that contain O? mysql> select ename from emp where ename like '%O%'; +-------+ | e ...

1. Insert data 1.1 practical problems Solution: use the INSERT statement to INSERT data into the table. 1.2 mode 1: add VALUES Using this syntax, only one piece of data can be inserted into the table at a time. Case 1: insert data in the default order for all fields of the table INSERT INTO Table name VALUES (value1,value2,....); In the ...

1, Processing of tabular data 1.1 ranking #The table connects itself, and then lists the results in turn to calculate the number of rows before each row (including which row itself) select A1.Name, A1.Sales,count(A2.Sales) Rank from Total_Sales A1, Total_Sales A2 where A2.Sales > A1.Sales or (A2.Sales = A1.Sales and A2.Name >= A1 ...

catalogue 1, DriverManager: drive management object 1. Register driver: tell the program which database driver jar to use 2. Get database connection: 2, Connection: database connection object 1. Get the object executing sql 2. Management services: 3, Statement: object to execute sql 1,boolean execute(String sql) : 2,int executeUpdate( ...

function flow ExecScan ExecScanFetch IndexNext[Top level loop function] [1]index_beginscan: (scandesc = index_beginscan generate scandesc (yes) index_beginscan_internal[getr] btbeginscan: initialization IndexScanDesc and BTScanOpaque IndexScanDesc scan = ... BTScanOpaque so = ... ...