2nd/10_Wiki/Dev/Topic_SQL/SQL_And.md

id, title, category, status, verification_status, canonical_id, aliases, duplicate_of, source_trust_level, confidence_score, created_at, updated_at, review_reason, merge_history, tags, raw_sources, applied_in, github_commit

id	title	category	status	verification_status	canonical_id	aliases	duplicate_of	source_trust_level	confidence_score	created_at	updated_at	review_reason	merge_history	tags	raw_sources	applied_in	github_commit
sql-and	SQL And	Database	draft	conceptual		SQL AND Operator AND operator SQL 논리곱		B	0.9	2026-07-04	2026-07-04			sql database w3schools and operators where	https://www.w3schools.com/sql/sql_and.asp

SQL And

🎯 한 줄 통찰 (One-line insight)

The AND operator filters records so that a row is returned only when ALL chained conditions in the WHERE clause are true. [S1]

🧠 핵심 개념 (Core concepts)

• AND operator — combines multiple conditions in a WHERE clause; a record is returned only if every condition is TRUE. [S1]
• Syntax — SELECT ... FROM table_name WHERE condition1 AND condition2 AND condition3 ...;. [S1]
• AND vs. OR — AND requires all conditions true; OR requires at least one condition true. [S1]
• Combining AND and OR — parentheses control evaluation grouping when mixing the two operators. [S1]

🧩 추출된 패턴 (Extracted patterns)

• Parenthesize when mixing AND/OR — WHERE Country = 'Spain' AND (CustomerName LIKE 'G%' OR CustomerName LIKE 'R%') gives the intended grouped result; omitting the parentheses changes which rows match because AND/OR precedence is not what the un-parenthesized reading suggests. [S1]

⚖️ 비교 및 선택 기준 (Comparison & decision criteria)

항목 (Option)	장점	단점	언제 선택
괄호로 그룹화	의도한 대로 정확한 결과, 가독성 향상	코드가 약간 길어짐	AND/OR를 섞어 쓸 때 항상
괄호 생략	짧음	연산자 우선순위로 인해 의도와 다른 결과가 나올 위험	단일 연산자만 사용할 때

📖 세부 내용 (Details)

• Filter on two conditions: SELECT * FROM Customers WHERE Country = 'Spain' AND CustomerName LIKE 'G%';. [S1]
• Filter on three conditions: WHERE Country = 'Brazil' AND City = 'Rio de Janeiro' AND CustomerID > 50;. [S1]
• Mixed AND/OR, correctly grouped with parentheses: WHERE Country = 'Spain' AND (CustomerName LIKE 'G%' OR CustomerName LIKE 'R%'); — without the parentheses, the same text returns a different (wider) result set, since it becomes "Spain AND starts-with-G" OR "starts-with-R regardless of country". [S1]

⚖️ 모순 및 업데이트 (Contradictions & updates)

소스에서 모순되는 정보는 발견되지 않음. 다만 괄호 유무에 따라 동일해 보이는 조건식이 다른 결과를 낼 수 있다는 점이 소스 내에서 직접 경고됨. [S1]

🛠️ 적용 사례 (Applied in summary)

현재 발견된 실제 적용 사례가 없습니다 — WHERE 절 다중 조건 필터링에서 OR/NOT과 함께 가장 빈번히 재사용되는 연산자다. [S1]

💻 코드 패턴 (Code patterns)

Multiple AND conditions (SQL):

SELECT * FROM Customers
WHERE Country = 'Brazil'
AND City = 'Rio de Janeiro'
AND CustomerID > 50;

Correctly grouped AND + OR (SQL):

SELECT * FROM Customers
WHERE Country = 'Spain' AND (CustomerName LIKE 'G%' OR CustomerName LIKE 'R%');

✅ 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 Where, SQL Or, SQL Not
• 참조 맥락: WHERE 절 다중 조건 결합의 기본 연산자 — OR/NOT과 세트로 이해해야 한다.

📚 출처 (Sources)

• [S1] W3Schools — SQL AND Operator — https://www.w3schools.com/sql/sql_and.asp

📝 변경 이력 (Change history)

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