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10_Wiki/Topic_Programming/Topic_SQL/SQL_Right_Join.md

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+---
+id: sql-right-join
+title: "SQL Right Join"
+category: "Database"
+status: "draft"
+verification_status: "conceptual"
+canonical_id: ""
+aliases: ["RIGHT JOIN", "RIGHT OUTER JOIN", "SQL 오른쪽 외부 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", "right-join"]
+raw_sources: ["https://www.w3schools.com/sql/sql_join_right.asp"]
+applied_in: []
+github_commit: ""
+---
+
+# [[SQL Right Join]]
+
+## 🎯 한 줄 통찰 (One-line insight)
+RIGHT JOIN is LEFT JOIN with the table roles mirrored — it keeps every row from the right table regardless of a match, filling unmatched left-table columns with NULL. [S1]
+
+## 🧠 핵심 개념 (Core concepts)
+- **RIGHT JOIN** — returns all rows from the right table (table2), and only the matched rows from the left table (table1); unmatched left-side columns become NULL. [S1]
+- **RIGHT JOIN == RIGHT OUTER JOIN** — the `OUTER` keyword is optional. [S1]
+- **Syntax** — `SELECT column_name(s) FROM table1 RIGHT JOIN table2 ON table1.column_name = table2.column_name;`. [S1]
+
+## 🧩 추출된 패턴 (Extracted patterns)
+- **LEFT/RIGHT symmetry** — a RIGHT JOIN can always be rewritten as a LEFT JOIN by swapping which table is written first; teams often standardize on LEFT JOIN alone for consistency (implied by RIGHT JOIN's comparative rarity in practice, though not stated verbatim in the source). [S1]
+
+## 📖 세부 내용 (Details)
+- All employees and any orders they placed (employees preserved even with zero orders): `SELECT Orders.OrderID, Employees.LastName, Employees.FirstName FROM Orders RIGHT JOIN Employees ON Orders.EmployeeID = Employees.EmployeeID ORDER BY Orders.OrderID;`. [S1]
+- The RIGHT JOIN keyword returns all records from the right table (Employees), even where there is no match in the left table (Orders). [S1]
+
+## ⚖️ 모순 및 업데이트 (Contradictions & updates)
+소스에서 모순되는 정보는 발견되지 않음.
+
+## 🛠️ 적용 사례 (Applied in summary)
+현재 발견된 실제 적용 사례가 없습니다 — "직원별 주문 실적(0건 포함)" 같은 리포트에서 전형적으로 쓰이는 패턴이다. [S1]
+
+## 💻 코드 패턴 (Code patterns)
+All rows from right table (SQL):
+```sql
+SELECT Orders.OrderID, Employees.LastName, Employees.FirstName
+FROM Orders
+RIGHT JOIN Employees ON Orders.EmployeeID = Employees.EmployeeID
+ORDER BY Orders.OrderID;
+```
+
+## ✅ 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 Full Join]]
+- **참조 맥락:** LEFT JOIN의 대칭 개념 — 오른쪽 테이블의 모든 행을 보존해야 할 때 사용.
+
+## 📚 출처 (Sources)
+- [S1] W3Schools — SQL RIGHT JOIN — https://www.w3schools.com/sql/sql_join_right.asp
+
+## 📝 변경 이력 (Change history)
+- 2026-07-04: Initial draft synthesized from the W3Schools "SQL RIGHT JOIN" page (Astra wiki-curation, P-Reinforce v3.1 format).