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-select-distinct
+title: "SQL Select Distinct"
+category: "Database"
+status: "draft"
+verification_status: "conceptual"
+canonical_id: ""
+aliases: ["SQL SELECT DISTINCT Statement", "DISTINCT keyword", "SQL 중복 제거"]
+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", "distinct", "select"]
+raw_sources: ["https://www.w3schools.com/sql/sql_distinct.asp"]
+applied_in: []
+github_commit: ""
+---
+
+# [[SQL Select Distinct]]
+
+## 🎯 한 줄 통찰 (One-line insight)
+SELECT DISTINCT returns only unique values from a column, collapsing duplicate rows that a plain SELECT would otherwise repeat. [S1]
+
+## 🧠 핵심 개념 (Core concepts)
+- **SELECT DISTINCT** — returns only distinct (unique) values, removing duplicate rows from the result. [S1]
+- **Syntax** — `SELECT DISTINCT column1, column2, ... FROM table_name;`. [S1]
+- **COUNT(DISTINCT column)** — counts the number of unique values in a column, but is not supported in Microsoft Access. [S1]
+
+## 🧩 추출된 패턴 (Extracted patterns)
+- **Dedup-then-count workaround** — for databases lacking `COUNT(DISTINCT ...)` (e.g. MS Access), wrap a `SELECT DISTINCT` subquery and `COUNT(*)` the outer result: `SELECT Count(*) AS DistinctCountries FROM (SELECT DISTINCT Country FROM Customers);`. [S1]
+
+## 📖 세부 내용 (Details)
+- Without DISTINCT, a query returns the column's value from every record, including repeats: `SELECT Country FROM Customers;`. [S1]
+- With DISTINCT, only unique values are returned: `SELECT DISTINCT Country FROM Customers;`. [S1]
+- Counting unique values directly: `SELECT COUNT(DISTINCT Country) FROM Customers;` — not supported on MS Access, which needs the subquery workaround above. [S1]
+
+## ⚖️ 모순 및 업데이트 (Contradictions & updates)
+- **DBMS 차이**: `COUNT(DISTINCT column_name)`이 MS Access에서는 지원되지 않는다는 점이 명시적으로 언급됨 — 방언별 차이가 존재. [S1]
+
+## 🛠️ 적용 사례 (Applied in summary)
+현재 발견된 실제 적용 사례가 없습니다 — 이후 COUNT() 챕터에서 DISTINCT와의 조합이 더 다뤄진다. [S1]
+
+## 💻 코드 패턴 (Code patterns)
+Select unique values (SQL):
+```sql
+SELECT DISTINCT Country FROM Customers;
+```
+Count unique values, MS Access-safe (SQL):
+```sql
+SELECT Count(*) AS DistinctCountries
+FROM (SELECT DISTINCT Country FROM Customers);
+```
+
+## ✅ 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 Select]], [[SQL Count]], [[SQL Group By]]
+- **참조 맥락:** SELECT 결과의 중복을 제거해야 할 때 참조하는 문서 — COUNT()와 결합해 고유값 개수를 셀 때 자주 함께 쓰인다.
+
+## 📚 출처 (Sources)
+- [S1] W3Schools — SQL SELECT DISTINCT Statement — https://www.w3schools.com/sql/sql_distinct.asp
+
+## 📝 변경 이력 (Change history)
+- 2026-07-04: Initial draft synthesized from the W3Schools "SQL SELECT DISTINCT Statement" page (Astra wiki-curation, P-Reinforce v3.1 format).