2nd/10_Wiki/Dev/Topic_SQL/SQL_Having.md

id, title, category, status, verification_status, canonical_id, aliases, duplicate_of, source_trust_level, confidence_score, created_at, updated_at, review_reason, merge_history, tags, raw_sources, applied_in, github_commit

id	title	category	status	verification_status	canonical_id	aliases	duplicate_of	source_trust_level	confidence_score	created_at	updated_at	review_reason	merge_history	tags	raw_sources	applied_in	github_commit
sql-having	SQL Having	Database	draft	conceptual		SQL HAVING Clause HAVING clause SQL 그룹 조건절		B	0.9	2026-07-04	2026-07-04			sql database w3schools having groupby aggregate	https://www.w3schools.com/sql/sql_having.asp

SQL Having

🎯 한 줄 통찰 (One-line insight)

HAVING filters GROUP BY results based on aggregate conditions, applying AFTER grouping — unlike WHERE, which filters individual rows BEFORE grouping. [S1]

🧠 핵심 개념 (Core concepts)

• HAVING clause — filters the results of a GROUP BY query based on aggregate functions. [S1]
• WHERE vs. HAVING — WHERE filters individual rows before grouping; HAVING filters groups after aggregation. [S1]
• Syntax — SELECT column1, aggregate_function(column2), column3, ... FROM table_name WHERE condition GROUP BY column1, column3 HAVING condition ORDER BY column_name;. [S1]

🧩 추출된 패턴 (Extracted patterns)

• WHERE + GROUP BY + HAVING composition — a query can filter rows first (WHERE), group them, then filter the resulting groups (HAVING) — e.g. restrict to two named employees, group by last name, then keep only groups with more than 25 orders. [S1]

📖 세부 내용 (Details)

• Countries with more than 5 customers: SELECT Country, COUNT(CustomerID) AS [Number of Customers] FROM Customers GROUP BY Country HAVING COUNT(CustomerID) > 5;. [S1]
• Same, sorted descending: ... GROUP BY Country HAVING COUNT(CustomerID) > 5 ORDER BY COUNT(CustomerID) DESC;. [S1]
• Employees with more than 10 orders, via JOIN + GROUP BY + HAVING: SELECT Employees.LastName, COUNT(Orders.OrderID) AS NumberOfOrders FROM Orders INNER JOIN Employees ON Orders.EmployeeID = Employees.EmployeeID GROUP BY LastName HAVING COUNT(Orders.OrderID) > 10;. [S1]
• Combined WHERE + GROUP BY + HAVING: filter to two named employees first, then keep only those with more than 25 orders. [S1]

⚖️ 모순 및 업데이트 (Contradictions & updates)

소스에서 모순되는 정보는 발견되지 않음.

🛠️ 적용 사례 (Applied in summary)

현재 발견된 실제 적용 사례가 없습니다 — "N건 이상인 그룹만 보기" 같은 리포팅 쿼리에서 GROUP BY와 항상 짝을 이뤄 쓰인다. [S1]

💻 코드 패턴 (Code patterns)

Filter groups by aggregate condition (SQL):

SELECT Country, COUNT(CustomerID) AS [Number of Customers]
FROM Customers
GROUP BY Country
HAVING COUNT(CustomerID) > 5;

✅ 검증 상태 및 신뢰도

• 상태: draft
• 검증 단계: conceptual
• 출처 신뢰도: B (W3Schools — widely used educational reference, not a primary standards body)
• 신뢰 점수: 0.90
• 중복 검사 결과: 신규 생성 (New discovery)

🔗 지식 그래프 (Knowledge Graph)

• 상위/루트: SQL Tutorial
• 관련 개념: SQL Group By, SQL Where, SQL Aggregate Functions
• 참조 맥락: GROUP BY 결과 자체를 조건으로 걸러야 할 때 사용 — WHERE와 역할을 혼동하지 않는 것이 핵심.

📚 출처 (Sources)

• [S1] W3Schools — SQL HAVING Clause — https://www.w3schools.com/sql/sql_having.asp

📝 변경 이력 (Change history)

• 2026-07-04: Initial draft synthesized from the W3Schools "SQL HAVING Clause" page (Astra wiki-curation, P-Reinforce v3.1 format).