Tag：Sentence
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Time：2021-5-11
Write a C / C + + program to execute two if else block statements at the same time. The syntax of if else statement in C / C + + language is as follows: If (Boolean expression) { //Statement execute only //If the Boolean expression is true } other { // […]
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Time：2021-5-11
（1） Branches If with else if, else Switch with case and default[difference] ① the comparison range of the former is written according to ‘bubble sort’, with more branches; ② The latter satisfies a specific value, has fewer branches and can be interrupted, and has higher execution efficiency. The value of ‘case’ is congruent （2） Cycle […]
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Time：2021-5-11
More interesting, please pay attention to official account number xhJaver 1、 Index data structure I will definitely ask this question during the interview. Why does MySQL choose B + tree as the index? Instead of selecting other indexes, such as B-tree? hash？ The following disk IO refers to the operation of loading data from the […]
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Time：2021-5-10
Author: Wang Zhibin, a former PGCE of China, is an official certified lecturer of PostgreSQL and a specially invited gold medal lecturer of Pangu cloud classroom. Pgbouncer has three pool modes: transaction pool, session pool and statement pool Transaction connection pool Database clients rarely execute continuous transactions without interruption. Instead, non database work is usually […]
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Time：2021-5-10
Connector Connector is responsible for establishing connection with client, obtaining permission, maintaining and managing connection 1. User password verification2. Query authority information and assign corresponding authority3. You can use show processlist to view the current connection4. If it has not been used for a long time, it will be disconnected automatically, and it will be […]
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Time：2021-5-9
Process control is an important part of the control logic direction and execution order of each programming language. Process control can be said to be the “Meridian” of a language. The most commonly used process control in go language areifandfor, andswitchandgotoIt is mainly a structure to simplify the code and reduce the duplication of code. […]
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Time：2021-5-8
catalogue preface Installation of virtual machine Commands and operations Basic command syntax Case sensitive SQL keyword and function name Column and Index Names alias Too long to see? Space Database connection Connection of SSMS Connection of command line Database operation establish delete constraint integrity constraint Common constraints NOT NULL UNIQUE PRIMARY KEY FOREIGN KEY DEFAULT […]
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Time：2021-5-7
The switch case statement replaces the long if statement that compares a variable to multiple integer values A switch statement is a multi branch statement. It provides a simple way to assign execution to different parts of the code based on the value of the expression. A switch is a control statement that allows a […]
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Time：2021-5-7
abstract: we call the “bad smell” in SQL the SQL statements that lead to inefficient execution and their execution methods. What is the bad taste in SQL SQL language is the standard language of relational database (RDB). Its function is to translate the user’s intention into a language that the database can understand. When human […]
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Time：2021-5-6
SQLite is an open source relational database, which is a SQL database engine with self-contained, zero configuration and transaction support. It is characterized by high portability, convenient use, compact structure, high efficiency and reliability. And SQLite is the most widely deployed SQL database engine in the world. SQLite source code is not subject to copyright […]
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Time：2021-5-6
Background of the problem MySQL master slave synchronization1. Structure: add, delete, change and query the business data of the master database, and the slave database is responsible for the query of the report2. Problem: the master-slave exception leads to inaccurate report data. During the online period, it occurs many times, and the synchronization has been […]
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Time：2021-5-5
1、 Operator 1. Arithmetic operator Arithmetic operator + – * / % ++ — Comparison operator > >= < <= != == === !== be careful: ————————————————- In the assignment operation: I + + means to first give the value of I to the left variable, and then add I on this basis++ ++I stands […]
