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-inner-join
+title: "SQL Inner Join"
+category: "Database"
+status: "draft"
+verification_status: "conceptual"
+canonical_id: ""
+aliases: ["INNER JOIN", "SQL 내부 조인"]
+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", "join", "inner-join"]
+raw_sources: ["https://www.w3schools.com/sql/sql_join_inner.asp"]
+applied_in: []
+github_commit: ""
+---
+
+# [[SQL Inner Join]]
+
+## 🎯 한 줄 통찰 (One-line insight)
+INNER JOIN — the default join type, so plain JOIN means the same thing — returns only rows that have a match in both tables, discarding anything unmatched. [S1]
+
+## 🧠 핵심 개념 (Core concepts)
+- **INNER JOIN** — returns only rows that have matching values in both tables. [S1]
+- **JOIN == INNER JOIN** — `JOIN` alone defaults to `INNER JOIN`; the parser treats them identically. [S1]
+- **Syntax** — `SELECT column_name(s) FROM table1 INNER JOIN table2 ON table1.column_name = table2.column_name;`. [S1]
+- **Multi-table INNER JOIN** — more than two tables can be joined by chaining multiple `INNER JOIN` clauses. [S1]
+
+## 🧩 추출된 패턴 (Extracted patterns)
+- **Table-name qualification is a good habit** — prefixing column names with their table (`Products.ProductID`) avoids ambiguity errors when the same column name (e.g. `CategoryID`) exists in both joined tables. [S1]
+- **Unmatched rows silently vanish** — a product with no `CategoryID`, or with a `CategoryID` absent from the Categories table, is simply excluded from the result — a common footgun when INNER JOIN is used where LEFT JOIN was intended. [S1]
+
+## 📖 세부 내용 (Details)
+- Basic two-table join: `SELECT ProductID, ProductName, CategoryName FROM Products INNER JOIN Categories ON Products.CategoryID = Categories.CategoryID;`. [S1]
+- Qualified column names to avoid ambiguity: `SELECT Products.ProductID, Products.ProductName, Categories.CategoryName FROM Products INNER JOIN Categories ON Products.CategoryID = Categories.CategoryID;`. [S1]
+- `JOIN` is shorthand for `INNER JOIN` — both produce identical results. [S1]
+- Joining three tables: `FROM Orders INNER JOIN Customers ON Orders.CustomerID = Customers.CustomerID INNER JOIN Shippers ON Orders.ShipperID = Shippers.ShipperID;`. [S1]
+
+## ⚖️ 모순 및 업데이트 (Contradictions & updates)
+소스에서 모순되는 정보는 발견되지 않음.
+
+## 🛠️ 적용 사례 (Applied in summary)
+현재 발견된 실제 적용 사례가 없습니다 — SQL Aliases 챕터의 테이블 별칭(c, o)이 INNER JOIN 예제에서도 그대로 재사용된다. [S1]
+
+## 💻 코드 패턴 (Code patterns)
+Two-table INNER JOIN (SQL):
+```sql
+SELECT Products.ProductID, Products.ProductName, Categories.CategoryName
+FROM Products
+INNER JOIN Categories ON Products.CategoryID = Categories.CategoryID;
+```
+Three-table INNER JOIN chain (SQL):
+```sql
+SELECT Orders.OrderID, Customers.CustomerName, Shippers.ShipperName
+FROM Orders
+INNER JOIN Customers ON Orders.CustomerID = Customers.CustomerID
+INNER JOIN Shippers ON Orders.ShipperID = Shippers.ShipperID;
+```
+
+## ✅ 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 Joins]], [[SQL Left Join]], [[SQL Aliases]]
+- **참조 맥락:** 매칭되는 행만 필요한 조인 쿼리의 기본 유형 — LEFT/RIGHT/FULL JOIN과 대비해서 이해해야 한다.
+
+## 📚 출처 (Sources)
+- [S1] W3Schools — SQL INNER JOIN — https://www.w3schools.com/sql/sql_join_inner.asp
+
+## 📝 변경 이력 (Change history)
+- 2026-07-04: Initial draft synthesized from the W3Schools "SQL INNER JOIN" page (Astra wiki-curation, P-Reinforce v3.1 format).