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-create-index
+title: "SQL Create Index"
+category: "Database"
+status: "draft"
+verification_status: "conceptual"
+canonical_id: ""
+aliases: ["SQL CREATE INDEX Statement", "CREATE INDEX", "CREATE UNIQUE INDEX"]
+duplicate_of: ""
+source_trust_level: "B"
+confidence_score: 0.88
+created_at: 2026-07-04
+updated_at: 2026-07-04
+review_reason: ""
+merge_history: []
+tags: ["sql", "database", "w3schools", "index"]
+raw_sources: ["https://www.w3schools.com/sql/sql_create_index.asp"]
+applied_in: []
+github_commit: ""
+---
+
+# [[SQL Create Index]]
+
+## 🎯 한 줄 통찰 (One-line insight)
+Indexes speed up data retrieval on frequently-searched columns, but slow down writes since the index itself must be updated — a classic read/write trade-off, not a free performance win. [S1]
+
+## 🧠 핵심 개념 (Core concepts)
+- **CREATE INDEX statement** — creates indexes on table columns to speed up data retrieval; invisible to users, purely a performance aid. [S1]
+- **Write cost trade-off** — updating indexed tables is more time-consuming, since indexes must also be updated — so index only columns that are frequently searched. [S1]
+- **Non-unique vs. unique** — `CREATE INDEX` allows duplicate values; `CREATE UNIQUE INDEX` does not. [S1]
+- **Multi-column index** — listing multiple columns creates a composite index. [S1]
+- **DROP INDEX** — vendor-specific syntax to remove an index. [S1]
+
+## ⚖️ 모순 및 업데이트 (Contradictions & updates)
+- **DROP INDEX 문법이 4가지 벤더 모두 다름**: SQL Server(`DROP INDEX table.index`), MySQL(`ALTER TABLE ... DROP INDEX`), MS Access(`DROP INDEX index ON table`), DB2/Oracle(`DROP INDEX index`). [S1]
+
+## 📖 세부 내용 (Details)
+- Non-unique index: `CREATE INDEX idx_lastname ON Persons (LastName);`. [S1]
+- Composite index: `CREATE INDEX idx_lname_fname ON Persons (LastName, FirstName);`. [S1]
+- Unique index syntax: `CREATE UNIQUE INDEX index_name ON table_name (column1, column2, ...);`. [S1]
+
+## 🛠️ 적용 사례 (Applied in summary)
+현재 발견된 실제 적용 사례가 없습니다 — 자주 검색되는 컬럼(예: LastName)에만 선택적으로 적용해야 쓰기 성능 저하를 최소화할 수 있다. [S1]
+
+## 💻 코드 패턴 (Code patterns)
+Single and composite index (SQL):
+```sql
+CREATE INDEX idx_lastname
+ON Persons (LastName);
+
+CREATE INDEX idx_lname_fname
+ON Persons (LastName, FirstName);
+```
+
+## ✅ 검증 상태 및 신뢰도
+- **상태:** draft
+- **검증 단계:** conceptual
+- **출처 신뢰도:** B (W3Schools — widely used educational reference, not a primary standards body)
+- **신뢰 점수:** 0.88
+- **중복 검사 결과:** 신규 생성 (New discovery)
+
+## 🔗 지식 그래프 (Knowledge Graph)
+- **상위/루트:** [[SQL Tutorial]]
+- **관련 개념:** [[SQL Constraints]], [[SQL Unique]], [[SQL Where]]
+- **참조 맥락:** 자주 검색되는 컬럼의 조회 성능을 높일 때 사용 — 쓰기 성능 저하와 트레이드오프임에 유의.
+
+## 📚 출처 (Sources)
+- [S1] W3Schools — SQL CREATE INDEX Statement — https://www.w3schools.com/sql/sql_create_index.asp
+
+## 📝 변경 이력 (Change history)
+- 2026-07-04: Initial draft synthesized from the W3Schools "SQL CREATE INDEX Statement" page (Astra wiki-curation, P-Reinforce v3.1 format).