2nd/10_Wiki/Dev/Topic_SQL/SQL_Aggregate_Functions.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-aggregate-functions	SQL Aggregate Functions	Database	draft	conceptual		Aggregate functions SQL 집계 함수		B	0.9	2026-07-04	2026-07-04			sql database w3schools aggregate groupby	https://www.w3schools.com/sql/sql_aggregate_functions.asp

SQL Aggregate Functions

🎯 한 줄 통찰 (One-line insight)

An aggregate function reduces a set of values to a single value, most often per GROUP BY group, and by convention ignores NULLs (except COUNT(*)). [S1]

🧠 핵심 개념 (Core concepts)

• Aggregate function — performs a calculation on a set of values and returns a single value. [S1]
• Common aggregate functions — MIN() (smallest value), MAX() (largest value), COUNT() (row count), SUM() (total), AVG() (average). [S1]
• Pairs with GROUP BY — GROUP BY splits the result-set into groups, and the aggregate function returns one value per group. [S1]
• NULL handling — aggregate functions ignore NULL values, except COUNT(*). [S1]

🧩 추출된 패턴 (Extracted patterns)

• NULL-exclusion is the default, COUNT(*) is the exception — every aggregate function silently skips NULLs, but COUNT(*) counts rows regardless of NULL content — a distinction worth remembering to avoid miscounted results. [S1]

📖 세부 내용 (Details)

이 문서는 개론 페이지로, 각 함수(MIN/MAX/COUNT/SUM/AVG)는 이어지는 개별 챕터에서 문법과 예제가 상세히 다뤄진다. [S1]

⚖️ 모순 및 업데이트 (Contradictions & updates)

소스에서 모순되는 정보는 발견되지 않음.

🛠️ 적용 사례 (Applied in summary)

현재 발견된 실제 적용 사례가 없습니다 — 이 개론 뒤에 MIN/MAX/COUNT/SUM/AVG 각각의 전용 챕터가 이어진다. [S1]

💻 코드 패턴 (Code patterns)

소스에 코드 예시 없음 (개론 페이지, 각 함수 챕터에서 코드 제공).

✅ 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 Min, SQL Max, SQL Count, SQL Sum, SQL Avg, SQL Group By
• 참조 맥락: MIN/MAX/COUNT/SUM/AVG 다섯 함수 챕터의 상위 개론 문서.

📚 출처 (Sources)

• [S1] W3Schools — SQL Aggregate Functions — https://www.w3schools.com/sql/sql_aggregate_functions.asp

📝 변경 이력 (Change history)

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