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Antigravity Agent e9cbf23ab5 docs(10_Wiki): Dev 폴더 누락분 반영 — Topic_Programming으로 통합

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  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.

2026-07-05 00:39:13 +09:00

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title

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):

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).

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