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preface We will show you a go zero micro service example in detail through a series of articles. The whole series is divided into ten articles, and the directory structure is as follows: Environment construction Service splitting User services Product service Order service Payment services (this article) RPC service Auth authen ...

In case of primary key conflict or unique key conflict in mysql, there are generally three avoidance methods according to different insertion strategies. 1,insert ignore 2,replace into 3,insert on duplicate key updateNote that unless the table has a PRIMARY KEY or UNIQUE index, using the above three statements is meaningless, which is the same ...

Index optimization and query optimization 1, Data preparation Insert 500000 entries in the student table and 10000 entries in the class table. Step 1: create a table #Class table CREATE TABLE `class` ( `id` INT(11) NOT NULL AUTO_INCREMENT, `className` VARCHAR(30) DEFAULT NULL, `address` VARCHAR(40) DEFAULT NULL, `monitor` INT NULL , PRIMARY ...

The original content of GreatSQL community cannot be used without authorization. Please contact Xiaobian and indicate the source for reprint.View modeIt is known that there are at least two ways to achieve this1. Turn on general_log can be observedOpen commandmysql> set global general_log=ON;Perform some operations[root@mgr2 ~]# mysql -uGrea ...

Sorting of data If sorting operation is not used, the data returned by query is displayed in the order of adding data by default. Sorting using the ORDER BY clause ASC (ascend): ascending (default)DESC (descend): descending The ORDER BY clause is at the end of the SELECT statement. Single column sorting For example: # Display employe ...

1. Arithmetic operator Arithmetic operators are mainly used for mathematical operations. They can connect two values or expressions before and after the operator, and perform addition (+), subtraction (-), multiplication (*), division (/) and modulus (%) operations on the values or expressions. 1. Addition and subtraction operators mysql> S ...

MySQL database 1. MySQL built-in functions 1.1 string function 1.1.1 concat splicing string function concat (parameter 1, parameter 2, parameter 3, parameter n) Parameters can be numbers or stringsConcatenate all parameters into a complete string Example 1: put 12334,'ab'Splice into a string'12334ab' select concat(12, 334, 'ab'); ...

File and data storageRun todo projectEnter app directoryapp ├── Dockerfile └── spec └── src └── yarn.lockSource code download: Getting started source code compressed packageNew DockerfileFROM node:12-alpine RUN sed -i 's/dl-cdn.alpinelinux.org/mirrors.ustc.edu.cn/g' /etc/apk/repositories RUN apk add --no-cache python3 g++ make RUN ...

24.23 total / statistical function 24.23.1 count   --How many students are there in a class?   --How many students have statistical mathematics scores greater than 90?   --How many people have a total score of more than 250?   --Difference between count(*) and count (column) --Explanation: count(*) returns the number o ...

scene Imagine that there is a requirement: design a comment system that requires users to comment on articles and reply to each other, without the limit of level.(the adjacency list most commonly used by programmers will not be discussed here. Partners can baidu by themselves.) Path Enumeration Path enumeration is a complete path composed of ...