• ## Exercises in Chapter 10 of statistical learning methods

Time：2021-11-29

• ## Leetcode MySQL exercise one – employees who exceed the manager’s income

Time：2021-10-23

The employee table contains all employees, and their managers also belong to employees. Each employee has an ID and a list of the ID of the manager corresponding to the employee. Id Name Salary ManagerId 1 Joe 70000 3 2 Henry 80000 4 3 Sam 60000 NULL 4 Max 90000 NULL The Department table contains […]

• ## Oracle (day 4)

Time：2021-4-29

1、 Distinct Syntax format: select distinct column name from table name 2、 Statistical function avg(x) count(1) count(*) max(x) min(x) sum(x) StdDev (x) to find the standard deviation of the value of X in a group of rows Variance (x) find the variance of x value in a group of rows Round and TRUNC: select round(avg(sal),4) […]

• ## Oracle (day 5)

Time：2021-4-28

Subquery 1. Single line subquery: For example: select * from EMP where Sal > (select Sal from EMP where ename =’allen ‘); 2. Multi row subquery: any all in Greater than any is greater than the minimum 　　select * from emp where sal>any(select sal from emp where deptno=10); 　　select * from emp where sal>(select min(sal) […]

• ## Missing lesson in Computer Education – MIT – L2 – shell tools and scripts

Time：2021-4-25

https://missing.csail.mit.edu/https://missing-semester-cn.g…https://www.bilibili.com/vide… note Shell script Special variables $0–Script name$1reach$9-Parameters of the script.$1Is the first parameter, and so on. [email protected] parameters $#-Number of parameters$?-The return value of the previous command -The process ID of the current script !!-Complete previous command, including parameters. Common application: when you fail to execute command due to insufficient authority, you […]

• ## PHP learning day 2 repl and package management

Time：2021-4-9

the latest version What is PHP in Debian wheel5.4Yes,day0It’s convenient to install it5.4. But look at the documentation5.5Yes, so I’ll use the latest version. Debian wheel hasdotdeb.orgprovidephp-5.5. It’s easy to install. The following will be added/etc/apt/sources.list: deb http://packages.dotdeb.org wheezy all deb-src http://packages.dotdeb.org wheezy all deb http://packages.dotdeb.org wheezy-php55 all deb-src http://packages.dotdeb.org wheezy-php55 all Add GPG key: […]

• ## Fragmented learning java outline

Time：2021-3-18

A series of articles： Fragmented learning java outline Fragmented learning Java (1) — the first Java program Fragmented learning Java (2) — Java annotation Fragmented learning Java (3) — Java defines variables Fragmented learning Java (4) — Java data types Fragmented learning Java (5) — calculating cylinder volume with Java Fragmented learning Java (6) — […]

• ## Break and continue, as well as exercises, handsome output 1 to 20

Time：2021-2-7

（44）break You can jump out of the current loop or switch （45）continue Enter the next cycle (46) exercise 1, handsome output 1 to 20 #include int main(void) { for(int i=1;i<=4;++i) { for(int j=1;i<=5;++j) { printf(“%5d”,j*i); } putchar(‘\n’); } return 0;

• ## Front end regular exercises

Time：2021-1-30

Exercises 1. Change get element by ID to hump name var str = ‘get-element-by-id’ const reg = /-\w/g const newStr = str.replace(reg, word => { console.log(word, ‘word12’) return word.substring(1).toUpperCase() }) console.log(newStr, ‘newStr’) // getElementById 2. Judge the telephone number function isPhone(tel) { var regx = /^1[34578]\d{9}\$/; return regx.test(tel); } 3. Find repeated words var str […]

• ## F # functional programming – Exercise answers

Time：2021-1-18

original texthttps://fsharpforfunandprofit.com/posts/computation-expressions-bind/ There is an exercise at the end of the original text let strToInt str = ??? let stringAddWorkflow x y z = yourWorkflow { let! a = strToInt x let! b = strToInt y let! c = strToInt z return a + b + c } // test1 let good = stringAddWorkflow “12” […]

• ## [learning notes] C language exercise: n people in a circle, arranged in sequence. Start counting from the first person (from 1 to 3). Anyone who reports 3 withdraws from the circle and asks the person who left the last number.

Time：2020-12-23

On the first day of the freshman year, do the exercises after class. (Chapter 8, question 5, Chapter 8, C programming, 5th Edition, by Tan Haoqiang) The specific title is shown in the title. First of all, I want to use an array to represent n individuals. First, the first n bits are initialized to […]