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title

SQL Full Join

🎯 한 줄 통찰 (One-line insight)

FULL JOIN unions the behavior of LEFT and RIGHT JOIN — it keeps every row from both tables, filling NULL wherever the other side has no match, and can return very large result sets. [S1]

🧠 핵심 개념 (Core concepts)

FULL JOIN — returns all rows when there is a match in either the left or right table. [S1]
NULL-filling both sides — an unmatched left row gets NULLs for all right-table columns, and vice versa. [S1]
FULL JOIN == FULL OUTER JOIN — the OUTER keyword is optional. [S1]
Syntax — SELECT column_name(s) FROM table1 FULL JOIN table2 ON table1.column_name = table2.column_name WHERE condition;. [S1]

🧩 추출된 패턴 (Extracted patterns)

Size warning — the source explicitly warns "FULL JOIN can potentially return very large result-sets!", making it something to use deliberately rather than by default. [S1]

📖 세부 내용 (Details)

All customers and all orders together, whether or not they match: SELECT Customers.CustomerName, Orders.OrderID FROM Customers FULL JOIN Orders ON Customers.CustomerID = Orders.CustomerID;. [S1]
Result includes rows with CustomerName = Null (orders with no matching customer) and rows with OrderID = Null (customers with no orders). [S1]

⚖️ 모순 및 업데이트 (Contradictions & updates)

소스에서 모순되는 정보는 발견되지 않음.

🛠️ 적용 사례 (Applied in summary)

현재 발견된 실제 적용 사례가 없습니다 — 데이터 정합성 점검(양쪽 테이블 모두에서 누락된 레코드 찾기)에 전형적으로 쓰이는 조인 유형이다. [S1]

💻 코드 패턴 (Code patterns)

Full outer join (SQL):

SELECT Customers.CustomerName, Orders.OrderID
FROM Customers
FULL JOIN Orders
ON Customers.CustomerID = Orders.CustomerID;

✅ 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 Right Join
참조 맥락: 양쪽 테이블의 unmatched 행을 모두 보존해야 하는 데이터 정합성 점검 쿼리.

📚 출처 (Sources)

[S1] W3Schools — SQL FULL JOIN — https://www.w3schools.com/sql/sql_join_full.asp

📝 변경 이력 (Change history)

2026-07-04: Initial draft synthesized from the W3Schools "SQL FULL JOIN" page (Astra wiki-curation, P-Reinforce v3.1 format).

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