docs(10_Wiki): 위키 구조 정리 — 언어 튜토리얼 카테고리 폴더 제거 + 신규 자산 동기화

Topic_CSS/Topic_HTML/Topic_JavaScript/Topic_Prompt/Topic_Comfyui 등 기존 카테고리 폴더를 정리하고, Topic_Graphic/Dev 등 신규 산출물과 Topics 내부 세션/메모리 기록을 동기화.
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+---
+id: sql-case
+title: "SQL Case"
+category: "Database"
+status: "draft"
+verification_status: "conceptual"
+canonical_id: ""
+aliases: ["SQL CASE Expression", "CASE expression", "SQL 조건식"]
+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", "case", "conditional"]
+raw_sources: ["https://www.w3schools.com/sql/sql_case.asp"]
+applied_in: []
+github_commit: ""
+---
+
+# [[SQL Case]]
+
+## 🎯 한 줄 통찰 (One-line insight)
+CASE works like an if-then-else chain inside a query — it stops at the first true condition, falls back to ELSE, and returns NULL if nothing matches and there's no ELSE. [S1]
+
+## 🧠 핵심 개념 (Core concepts)
+- **CASE expression** — defines different results based on specified conditions within an SQL statement. [S1]
+- **Short-circuit evaluation** — stops at the first true condition and returns its result, like an if-then-else statement. [S1]
+- **ELSE fallback** — if no condition is true, returns the ELSE value; without ELSE and no match, returns NULL. [S1]
+- **Syntax** — `CASE WHEN condition1 THEN result1 WHEN condition2 THEN result2 ... ELSE default_result END;`. [S1]
+
+## 📖 세부 내용 (Details)
+- Categorize products by price into a new derived column: [S1]
+```sql
+SELECT ProductName, Price,
+CASE
+    WHEN Price < 20 THEN 'Low Cost'
+    WHEN Price BETWEEN 20 AND 50 THEN 'Medium Cost'
+    ELSE 'High Cost'
+END AS PriceCategory
+FROM Products;
+```
+
+## ⚖️ 모순 및 업데이트 (Contradictions & updates)
+소스에서 모순되는 정보는 발견되지 않음.
+
+## 🛠️ 적용 사례 (Applied in summary)
+현재 발견된 실제 적용 사례가 없습니다 — 가격 구간처럼 값을 범주화하는 파생 컬럼을 만들 때 전형적으로 쓰인다. [S1]
+
+## 💻 코드 패턴 (Code patterns)
+CASE for value categorization (SQL):
+```sql
+SELECT ProductName, Price,
+CASE
+    WHEN Price < 20 THEN 'Low Cost'
+    WHEN Price BETWEEN 20 AND 50 THEN 'Medium Cost'
+    ELSE 'High Cost'
+END AS PriceCategory
+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 Between]], [[SQL Aliases]], [[SQL Null Functions]]
+- **참조 맥락:** 값 기반 분기/범주화 파생 컬럼이 필요한 모든 쿼리의 기본 조건식.
+
+## 📚 출처 (Sources)
+- [S1] W3Schools — SQL CASE Expression — https://www.w3schools.com/sql/sql_case.asp
+
+## 📝 변경 이력 (Change history)
+- 2026-07-04: Initial draft synthesized from the W3Schools "SQL CASE Expression" page (Astra wiki-curation, P-Reinforce v3.1 format).