docs(10_Wiki): Dev 폴더 누락분 반영 — Topic_Programming으로 통합

이전 재구성 작업에서 Dev/ 폴더가 누락되었던 것을 반영. - Dev/Topic_Programming(중첩 폴더, 78개)은 Dev 자체 최상위 폴더들 (Architecture/Conventions/Engineering_Intelligence 등)과 완전 중복이라 제거. - Dev 최상위 엔지니어링 지식 폴더(Architecture/Conventions/Engineering_Intelligence/ Failure_Library/Generalized_Principles/Language/Pattern_Catalog/Platform_Guides/ Subsystems, 77개)는 이미 Topic_Programming/Topic_Programming에 더 최신 버전이 존재해 중복 제거(고유 콘텐츠 1개는 예외 처리하여 이동 보존). - Dev의 W3Schools 언어 튜토리얼 폴더(Topic_C/CPP/CSS/CSharp/HOWTO/HTML/Java/ JavaScript/PHP/Python/SQL/W3CSS, 1201개)는 전부 Topic_Programming 하위로 이동. - 에이전트 운영 상태(.astra/docs)는 그대로 유지, 콘텐츠 폴더만 정리. - Topic_Programming 최종 문서 수: 2784 → 3985.
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+---
+id: sql-avg
+title: "SQL Avg"
+category: "Database"
+status: "draft"
+verification_status: "conceptual"
+canonical_id: ""
+aliases: ["SQL AVG() Function", "AVG function", "SQL 평균"]
+duplicate_of: ""
+source_trust_level: "B"
+confidence_score: 0.9
+created_at: 2026-07-04
+updated_at: 2026-07-04
+review_reason: ""
+merge_history: []
+tags: ["sql", "database", "w3schools", "avg", "aggregate"]
+raw_sources: ["https://www.w3schools.com/sql/sql_avg.asp"]
+applied_in: []
+github_commit: ""
+---
+
+# [[SQL Avg]]
+
+## 🎯 한 줄 통찰 (One-line insight)
+AVG() returns a numeric column's mean, ignoring NULLs, and doubles as a comparison baseline when nested as a subquery in a WHERE clause. [S1]
+
+## 🧠 핵심 개념 (Core concepts)
+- **AVG() function** — returns the average value of a numeric column; ignores NULL values. [S1]
+- **Syntax** — `SELECT AVG(column_name) FROM table_name WHERE condition;`. [S1]
+- **AVG() with GROUP BY** — returns the average per group. [S1]
+
+## 🧩 추출된 패턴 (Extracted patterns)
+- **AVG() as a subquery baseline** — `WHERE Price > (SELECT AVG(Price) FROM Products)` uses AVG() inside a subquery to compare each row against the overall average — a reusable pattern for "above/below average" filters. [S1]
+
+## 📖 세부 내용 (Details)
+- Basic average: `SELECT AVG(Price) FROM Products;`. [S1]
+- With WHERE: `SELECT AVG(Price) FROM Products WHERE CategoryID = 1;`. [S1]
+- With alias: `SELECT AVG(Price) AS [average price] FROM Products;`. [S1]
+- Above-average filter via subquery: `SELECT * FROM Products WHERE Price > (SELECT AVG(Price) FROM Products);`. [S1]
+- With GROUP BY: `SELECT AVG(Price) AS AveragePrice, CategoryID FROM Products GROUP BY CategoryID;`. [S1]
+
+## ⚖️ 모순 및 업데이트 (Contradictions & updates)
+소스에서 모순되는 정보는 발견되지 않음.
+
+## 🛠️ 적용 사례 (Applied in summary)
+현재 발견된 실제 적용 사례가 없습니다 — "평균 이상/이하" 필터링은 실무 리포트에서 흔한 패턴이다. [S1]
+
+## 💻 코드 패턴 (Code patterns)
+Above-average filter using AVG() as subquery (SQL):
+```sql
+SELECT * FROM Products
+WHERE Price > (SELECT AVG(Price) FROM Products);
+```
+
+## ✅ 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 Aggregate Functions]], [[SQL Group By]], [[SQL Where]]
+- **참조 맥락:** 평균값 계산 및 평균 대비 비교 필터링의 기본 함수.
+
+## 📚 출처 (Sources)
+- [S1] W3Schools — SQL AVG() Function — https://www.w3schools.com/sql/sql_avg.asp
+
+## 📝 변경 이력 (Change history)
+- 2026-07-04: Initial draft synthesized from the W3Schools "SQL AVG() Function" page (Astra wiki-curation, P-Reinforce v3.1 format).