3. GROUP BY & HAVING.md

GROUP BY

---

예제 테이블

users

id	name	language_id	framework_id
1	Jo	1	1
2	Min	1	10
3	Kuk	3	3
4	Like	4	4
5	Lion	5	5
6	Dev	6	6
7	Dogs	7	7

languages

id	language
1	Java
3	TypeScript
4	Ruby
5	Python
6	Swift
7	Kotlin
8	JavaScript

framewords

id	frameworkName
1	Spring MVC
2	Angular
3	Rails
4	Django

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SQL Example

SELECT l.languageName, COUNT(language_id) count
FROM users u
INNER JOIN languages l ON u.language_id = l.id
GROUP BY l.languageName;

결과 테이블

languageName	count
Java	2
Kotlin	1
Python	1
Ruby	1
Swift	1
TypeScript	1

HAVING

SELECT l.languageName, COUNT(language_id) count
FROM users u
INNER JOIN languages l ON u.language_id = l.id
GROUP BY l.languageName
HAVING count > 1;

결과 테이블

languageName	count
Java	2