---
id: sql-case
title: "SQL Case"
category: "Database"
status: "draft"
verification_status: "conceptual"
canonical_id: ""
aliases: ["SQL CASE Expression", "CASE expression", "SQL 조건식"]
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", "case", "conditional"]
raw_sources: ["https://www.w3schools.com/sql/sql_case.asp"]
applied_in: []
github_commit: ""
---

# [[SQL Case]]

## 🎯 한 줄 통찰 (One-line insight)
CASE works like an if-then-else chain inside a query — it stops at the first true condition, falls back to ELSE, and returns NULL if nothing matches and there's no ELSE. [S1]

## 🧠 핵심 개념 (Core concepts)
- **CASE expression** — defines different results based on specified conditions within an SQL statement. [S1]
- **Short-circuit evaluation** — stops at the first true condition and returns its result, like an if-then-else statement. [S1]
- **ELSE fallback** — if no condition is true, returns the ELSE value; without ELSE and no match, returns NULL. [S1]
- **Syntax** — `CASE WHEN condition1 THEN result1 WHEN condition2 THEN result2 ... ELSE default_result END;`. [S1]

## 📖 세부 내용 (Details)
- Categorize products by price into a new derived column: [S1]
```sql
SELECT ProductName, Price,
CASE
    WHEN Price < 20 THEN 'Low Cost'
    WHEN Price BETWEEN 20 AND 50 THEN 'Medium Cost'
    ELSE 'High Cost'
END AS PriceCategory
FROM Products;
```

## ⚖️ 모순 및 업데이트 (Contradictions & updates)
소스에서 모순되는 정보는 발견되지 않음.

## 🛠️ 적용 사례 (Applied in summary)
현재 발견된 실제 적용 사례가 없습니다 — 가격 구간처럼 값을 범주화하는 파생 컬럼을 만들 때 전형적으로 쓰인다. [S1]

## 💻 코드 패턴 (Code patterns)
CASE for value categorization (SQL):
```sql
SELECT ProductName, Price,
CASE
    WHEN Price < 20 THEN 'Low Cost'
    WHEN Price BETWEEN 20 AND 50 THEN 'Medium Cost'
    ELSE 'High Cost'
END AS PriceCategory
FROM Products;
```

## ✅ 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 Between]], [[SQL Aliases]], [[SQL Null Functions]]
- **참조 맥락:** 값 기반 분기/범주화 파생 컬럼이 필요한 모든 쿼리의 기본 조건식.

## 📚 출처 (Sources)
- [S1] W3Schools — SQL CASE Expression — https://www.w3schools.com/sql/sql_case.asp

## 📝 변경 이력 (Change history)
- 2026-07-04: Initial draft synthesized from the W3Schools "SQL CASE Expression" page (Astra wiki-curation, P-Reinforce v3.1 format).