[๋‹ฌ๋ฆฌ๊ธฐ๋ฐ˜] Lv1. ๋žœ๋ค ๋‹‰๋„ค์ž„ ์ƒ์„ฑ๊ธฐ
ยท
๋‚ด์ผ๋ฐฐ์›€์บ ํ”„/์‚ฌ์ „์บ ํ”„ ๊ณผ์ œ
๋žœ๋คํ•œ ๋‹‰๋„ค์ž„์„ ์ƒ์„ฑํ•˜๋Š” ์ž๋ฐ” ์ฝ”๋“œ๋ฅผ ์ž‘์„ฑํ•ด๋ณด์„ธ์š”. ์‚ฌ์šฉ์ž๋Š” ์ตœ์†Œ 27๊ฐ€์ง€ ์ด์ƒ์˜ ๋‹‰๋„ค์ž„ ์ค‘ ํ•˜๋‚˜๋ฅผ ๋žœ๋ค์œผ๋กœ ์ถœ๋ ฅ ํ•  ์ˆ˜ ์žˆ์Šต๋‹ˆ๋‹ค. (์•„๋ž˜์˜ ํ‚ค์›Œ๋“œ๋ฅผ ์‚ฌ์šฉํ•ด์ฃผ์„ธ์š”!) - ๊ธฐ์ฒ ์ดˆํ’, ๋ฉ‹์žˆ๋Š”, ์žฌ๋ฏธ์žˆ๋Š” - ๋„์ „์ ์ธ, ๋…ธ๋ž€์ƒ‰์˜, ๋ฐ”๋ณด๊ฐ™์€ - ๋Œ๊ณ ๋ž˜, ๊ฐœ๋ฐœ์ž, ์˜ค๋ž‘์šฐํƒ„  ์ž‘์„ฑ์ฝ”๋“œ๋‚˜์˜ ๋‹ตimport java.util.*;import java.lang.*;import java.io.*;// The main method must be in a class named "Main".class Main { public static void main(String[] args) { //3๊ฐœ์˜ ๋ฐฐ์—ด ์ƒ์„ฑ String[] first = {"๊ธฐ์ ˆ์ดˆํ’","๋ฉ‹์žˆ๋Š”","์žฌ๋ฏธ์žˆ๋Š”"}; String..
[๊ฑท๊ธฐ๋ฐ˜] ๋ฐ˜๋ณต๋ฌธ ์—ฐ์Šตํ•˜๊ธฐ Part 3
ยท
๋‚ด์ผ๋ฐฐ์›€์บ ํ”„/์‚ฌ์ „์บ ํ”„ ๊ณผ์ œ
๊ตฌ๊ตฌ๋‹จ ์ถœ๋ ฅํ•˜๊ธฐ2๋‹จ๋ถ€ํ„ฐ 9๋‹จ๊นŒ์ง€์˜ ๊ตฌ๊ตฌ๋‹จ์„ ์ถœ๋ ฅํ•˜์„ธ์š”.ํžŒํŠธ : ์ค‘์ฒฉ ๋ฐ˜๋ณต๋ฌธ [๋‚˜์˜ ๋‹ต1 - For ์‚ฌ์šฉ]class Main { public static void main(String[] args) { for(int i=2; i  [๋‚˜์˜ ๋‹ต2 - while ์‚ฌ์šฉ]class Main { public static void main(String[] args) { int i=2; while(i
[๊ฑท๊ธฐ๋ฐ˜] ๋ฐ˜๋ณต๋ฌธ ์—ฐ์Šตํ•˜๊ธฐ Part 2
ยท
๋‚ด์ผ๋ฐฐ์›€์บ ํ”„/์‚ฌ์ „์บ ํ”„ ๊ณผ์ œ
1๋ถ€ํ„ฐ 100๊นŒ์ง€์˜ ์ง์ˆ˜๋งŒ ์ถœ๋ ฅํ•˜๊ธฐ๋ฐ˜๋ณต๋ฌธ์„ ์‚ฌ์šฉํ•˜์—ฌ 1๋ถ€ํ„ฐ 100๊นŒ์ง€์˜ ์ˆซ์ž ์ค‘ ์ง์ˆ˜๋งŒ ์ถœ๋ ฅํ•˜์„ธ์š”. [๋‚˜์˜ ๋‹ต1 - For ์‚ฌ์šฉ]class Main { public static void main(String[] args) { for(int i=2; i  [๋‚˜์˜ ๋‹ต2 - while ์‚ฌ์šฉ]class Main { public static void main(String[] args) { int i=2; while(i[๋ฉ”๋ชจ]i+=2๋Š” i=i+2์™€ ๊ฐ™์€ ์˜๋ฏธ์ด๋‹ค.
[๊ฑท๊ธฐ๋ฐ˜] ๋ฐ˜๋ณต๋ฌธ ์—ฐ์Šตํ•˜๊ธฐ Part 1
ยท
๋‚ด์ผ๋ฐฐ์›€์บ ํ”„/์‚ฌ์ „์บ ํ”„ ๊ณผ์ œ
1๋ถ€ํ„ฐ 100๊นŒ์ง€์˜ ์ˆซ์ž ์ถœ๋ ฅํ•˜๊ธฐfor ๋˜๋Š” while ๋ฐ˜๋ณต๋ฌธ์„ ์‚ฌ์šฉํ•˜์—ฌ 1๋ถ€ํ„ฐ 100๊นŒ์ง€์˜ ์ˆซ์ž๋ฅผ ์ถœ๋ ฅํ•˜์„ธ์š”. [๋‚˜์˜ ๋‹ต1 - For ์‚ฌ์šฉ]class Main { public static void main(String[] args) { for(int i=1; i  [๋‚˜์˜ ๋‹ต2 - while ์‚ฌ์šฉ]class Main { public static void main(String[] args) { int i=1; while(i
[๊ฑท๊ธฐ๋ฐ˜] Java ์•Œ์•„๋ณด๊ธฐ
ยท
๋‚ด์ผ๋ฐฐ์›€์บ ํ”„/์‚ฌ์ „์บ ํ”„ ๊ณผ์ œ
1. Java ๋ž€? ' https://www.ibm.com/kr-ko/topics/java '๋ฅผ ์ฝ์–ด๋ณด๊ณ  ๋‚ด์šฉ ์ •๋ฆฌํ•˜๊ธฐ  Java์˜ ํŠน์ง•  ๋…ธํŠธ๋ถ ์ปดํ“จํ„ฐ, ๋ชจ๋ฐ”์ผ ๋””๋ฐ”์ด์Šค ๋“ฑ ์ˆ˜์‹ญ์–ต๊ฐœ์˜ ์žฅ์น˜์—์„œ ์‹คํ–‰๋˜๋Š” ๊ฐ์ฒด ์ง€ํ–ฅ ํ”„๋กœ๊ทธ๋ž˜๋ฐ ์–ธ์–ด ๋ฐ ์†Œํ”„ํŠธ ์›จ์–ด ํ”Œ๋žซํผJava์˜ ๊ทœ์น™๊ณผ ๊ตฌ๋ฌธ์€ C / C++ ์–ธ์–ด๋ฅผ ๊ธฐ๋ฐ˜์šฉ์–ด ์ •๋ฆฌ- JDK(Java Development Kit) : ์ž๋ฐ” ๊ฐœ๋ฐœ ๋„๊ตฌ- JRE(Java Runtime Environment) : ์ž๋ฐ” ์‹คํ–‰ ํ™˜๊ฒฝ- JVM(Java Virtual Machine ) : JRE์˜ ์ผ๋ถ€, ์ž๋ฐ” ๊ฐ€์ƒ ๊ธฐ๊ณ„- Java ๋ฐ”์ดํŠธ ์ฝ”๋“œ : JVM์„ ์œ„ํ•œ ๋ช…๋ น์–ด ์ง‘ํ•ฉ, JVM์„ ์ง€์›ํ•˜๋Š” ๋ชจ๋“  ์‹œ์Šคํ…œ์—์„œ ์ˆ˜์ • ์—†์ด ์‹คํ–‰๋จ  Java์˜ ์žฅ์   ๊ด‘๋ฒ”์œ„ํ•œ ํ™œ์šฉ: ์Šค๋งˆํŠธํฐ Android ์šด์˜..
[๋‹ฌ๋ฆฌ๊ธฐ๋ฐ˜] SQL ๋ฌธ๋ฒ• ์—ฐ์Šต 7
ยท
๋‚ด์ผ๋ฐฐ์›€์บ ํ”„/์‚ฌ์ „์บ ํ”„ ๊ณผ์ œ
LV5. ์˜ˆ์‚ฐ์ด ๊ฐ€์žฅ ํฐ ํ”„๋กœ์ ํŠธ๋Š”? ๋‚ด๊ฐ€ ํ‹€๋ฆฐ/๋†“์นœ ๋ถ€๋ถ„์€ ๋ฏผํŠธ์ƒ‰์œผ๋กœ ํ‘œ์‹œ!  1. ๊ฐ ์ง์›์ด ์†ํ•œ ๋ถ€์„œ์—์„œ ๊ฐ€์žฅ ๋†’์€ ์›”๊ธ‰์„ ๋ฐ›๋Š” ์ง์›๋“ค๋งŒ ํฌํ•จ๋œ ๊ฒฐ๊ณผ๋ฅผ ์กฐํšŒํ•˜๋Š” SQL ์ฟผ๋ฆฌ๋ฅผ ์ž‘์„ฑํ•ด์ฃผ์„ธ์š”. a.  ์ถœ๋ ฅ ๊ฒฐ๊ณผ์—๋Š” ์ง์›์˜ ์ด๋ฆ„, ๋ถ€์„œ, ๊ทธ๋ฆฌ๊ณ  ์›”๊ธ‰์ด ํฌํ•จ๋˜์–ด์•ผ ํ•ฉ๋‹ˆ๋‹ค. ๋‚˜์˜ ๋‹ตselect e.Name, e.Department, e.Salaryfrom eemployees e left join(select Department, max(salary) max_salfrom eemployees group by 1) a on e.Department=a.Departmentwhere e.Salary=a.max_sal์ •๋‹ตSELECT e.Name, e.Department, e.SalaryFROM Employees e..
[๋‹ฌ๋ฆฌ๊ธฐ๋ฐ˜] SQL ๋ฌธ๋ฒ• ์—ฐ์Šต 6
ยท
๋‚ด์ผ๋ฐฐ์›€์บ ํ”„/์‚ฌ์ „์บ ํ”„ ๊ณผ์ œ
Lv5. ๊ฐ€์žฅ ๋งŽ์ด ํŒ”๋ฆฐ ํ’ˆ๋ชฉ์€? ๋‚ด๊ฐ€ ํ‹€๋ฆฐ/๋†“์นœ ๋ถ€๋ถ„์€ ๋ฏผํŠธ์ƒ‰์œผ๋กœ ํ‘œ์‹œ!  1. ๊ฐ ๊ณ ๊ฐ์ด ๊ตฌ๋งคํ•œ ๋ชจ๋“  ์ œํ’ˆ์˜ ์ด ๊ธˆ์•ก์„ ๊ณ„์‚ฐํ•˜๊ณ , ๊ณ ๊ฐ ์ด๋ฆ„, ์ด ๊ตฌ๋งค ๊ธˆ์•ก, ์ฃผ๋ฌธ ์ˆ˜๋ฅผ ์ถœ๋ ฅํ•˜๋Š” SQL ์ฟผ๋ฆฌ๋ฅผ ์ž‘์„ฑํ•ด์ฃผ์„ธ์š”.๋‚˜์˜ ๋‹ตselect customerName,sum(total) TotalAmount,count(*) OrderCountfrom(select o.CustomerID,p.Price,o.Quantity,p.Price*o.Quantity totalfrom Orders o inner join products p on o.ProductID=p.ProductID) a join Customers c on a.CustomerID=c.CustomerIDgroup by 1์ •๋‹ตSELECT c.CustomerName, ..
[๋‹ฌ๋ฆฌ๊ธฐ๋ฐ˜] SQL ๋ฌธ๋ฒ• ์—ฐ์Šต 5
ยท
๋‚ด์ผ๋ฐฐ์›€์บ ํ”„/์‚ฌ์ „์บ ํ”„ ๊ณผ์ œ
Lv4. ๊ฐ€์žฅ ๋†’์€ ์›”๊ธ‰์„ ๋ฐ›๋Š” ์ง์›์€?  ๋‚ด๊ฐ€ ํ‹€๋ฆฐ/๋†“์นœ ๋ถ€๋ถ„์€ ๋ฏผํŠธ์ƒ‰์œผ๋กœ ํ‘œ์‹œ!  1. ๊ฐ ์ง์›์˜ ์ด๋ฆ„, ๋ถ€์„œ, ์›”๊ธ‰, ๊ทธ๋ฆฌ๊ณ  ๊ทธ ์ง์›์ด ์†ํ•œ ๋ถ€์„œ์—์„œ ๊ฐ€์žฅ ๋†’์€ ์›”๊ธ‰์„ ๋ฐ›๊ณ  ์žˆ๋Š” ์ง์›์˜ ์ด๋ฆ„๊ณผ ์›”๊ธ‰์„ ์กฐํšŒํ•˜๋Š” SQL ์ฟผ๋ฆฌ๋ฅผ ์ž‘์„ฑํ•ด์ฃผ์„ธ์š”. ๋‚˜์˜ ๋‹ตselect e2.Name, e2.Department, e2.Salary, sub.Top_Earner, sub.Top_Salaryfrom Employees e2 JOIN(select e.Department, e.Name Top_Earner, a.Top_salaryfrom Employees e join (select Department, max(Salary) Top_salaryfrom Employeesgroup by Department) a on e.Depar..
[๋‹ฌ๋ฆฌ๊ธฐ๋ฐ˜] SQL ๋ฌธ๋ฒ• ์—ฐ์Šต 4
ยท
๋‚ด์ผ๋ฐฐ์›€์บ ํ”„/์‚ฌ์ „์บ ํ”„ ๊ณผ์ œ
Lv4. ๋‹จ๊ณจ ๊ณ ๊ฐ๋‹˜ ์ฐพ๊ธฐ ๋‚ด๊ฐ€ ํ‹€๋ฆฐ/๋†“์นœ ๋ถ€๋ถ„์€ ๋ฏผํŠธ์ƒ‰์œผ๋กœ ํ‘œ์‹œ!  1. ๊ณ ๊ฐ๋ณ„๋กœ ์ฃผ๋ฌธ ๊ฑด์ˆ˜์™€ ์ด ์ฃผ๋ฌธ ๊ธˆ์•ก์„ ์กฐํšŒํ•˜๋Š” SQL ์ฟผ๋ฆฌ๋ฅผ ์ž‘์„ฑํ•ด์ฃผ์„ธ์š”.  a. ์ถœ๋ ฅ ๊ฒฐ๊ณผ์—๋Š” ๊ณ ๊ฐ ์ด๋ฆ„, ์ฃผ๋ฌธ ๊ฑด์ˆ˜, ์ด ์ฃผ๋ฌธ ๊ธˆ์•ก์ด ํฌํ•จ๋˜์–ด์•ผ ํ•ฉ๋‹ˆ๋‹ค. ๋‹จ, ์ฃผ๋ฌธ์„ ํ•œ ์ ์ด ์—†๋Š” ๊ณ ๊ฐ๋„ ๊ฒฐ๊ณผ์— ํฌํ•จ๋˜์–ด์•ผ ํ•ฉ๋‹ˆ๋‹ค.๋‚˜์˜ ๋‹ตSelect CustomerName, count(o.OrderID) OrderCount, sum(o.TotalAmount) TotalSpentFrom Customers c LEFT JOIN Orders o ON c.CustomerID = o.CustomerIDGroup by 1์ •๋‹ตSELECT c.CustomerName, COUNT(o.OrderID) AS OrderCount, COALESCE(SUM(o.Tot..
[๋‹ฌ๋ฆฌ๊ธฐ๋ฐ˜] SQL ๋ฌธ๋ฒ• ์—ฐ์Šต 3
ยท
๋‚ด์ผ๋ฐฐ์›€์บ ํ”„/์‚ฌ์ „์บ ํ”„ ๊ณผ์ œ
Lv3. ์ด์šฉ์ž์˜ ํฌ์ธํŠธ ์กฐํšŒํ•˜๊ธฐ ๋‚ด๊ฐ€ ํ‹€๋ฆฐ/๋†“์นœ ๋ถ€๋ถ„์€ ๋ฏผํŠธ์ƒ‰์œผ๋กœ ํ‘œ์‹œ!  ์ƒํ™ฉ: ์ด๋ฒˆ์—๋Š” ์ด์šฉ์ž๋“ค ๋ณ„๋กœ ํš๋“ํ•œ ํฌ์ธํŠธ๋ฅผ ํ•™์ƒ๋“ค์—๊ฒŒ ์ด๋ฉ”์ผ๋กœ ๋ณด๋‚ด๋ ค๊ณ  ํ•ฉ๋‹ˆ๋‹ค. ์ด๋ฅผ ์œ„ํ•œ ์ž๋ฃŒ๋ฅผ ๊ฐ€๊ณตํ•ด๋ด…์‹œ๋‹ค. ํŠนํžˆ users ํ…Œ์ด๋ธ”์—๋Š” ์žˆ์œผ๋‚˜ point_users ์—๋Š” ์—†๋Š” ์œ ์ €๊ฐ€ ์žˆ์–ด์š”. ์ด ์œ ์ €๋“ค์˜ ๊ฒฝ์šฐ point๋ฅผ 0์œผ๋กœ ์ฒ˜๋ฆฌํ•ฉ์‹œ๋‹ค.๋‚˜์˜ ๋‹ตselect u.user_id, u.email, coalesce(p.point,0) pointfrom users u left join point_users p on u.user_id=p.user_idorder by 3 desc์ •๋‹ตSELECT u.user_id, u.email, COALESCE(p.point,0) as pointFROM users uleft JOIN point..