---
id: sql-update
title: "SQL Update"
category: "Database"
status: "draft"
verification_status: "conceptual"
canonical_id: ""
aliases: ["SQL UPDATE Statement", "UPDATE statement", "SQL 수정"]
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", "update"]
raw_sources: ["https://www.w3schools.com/sql/sql_update.asp"]
applied_in: []
github_commit: ""
---

# [[SQL Update]]

## 🎯 한 줄 통찰 (One-line insight)
UPDATE modifies existing records, and omitting its WHERE clause is a critical footgun that silently rewrites every row in the table. [S1]

## 🧠 핵심 개념 (Core concepts)
- **UPDATE statement** — updates or modifies one or more existing records in a table. [S1]
- **Syntax** — `UPDATE table_name SET column1 = value1, column2 = value2, ... WHERE condition;`. [S1]
- **WHERE determines scope** — the WHERE clause specifies exactly which record(s) get updated. [S1]

## 🧩 추출된 패턴 (Extracted patterns)
- **Missing-WHERE footgun** — the source explicitly warns: omit WHERE and ALL records in the table are updated. This is called out twice (as a "Note" and as an "Update Warning!") — a strong signal that this is the most common and costly mistake with this statement. [S1]

## 📖 세부 내용 (Details)
- Update a single record: `UPDATE Customers SET ContactName = 'Alfred Schmidt', City= 'Frankfurt' WHERE CustomerID = 1;`. [S1]
- Update multiple records matching a condition: `UPDATE Customers SET ContactName='Juan' WHERE Country='Mexico';`. [S1]
- Update ALL records (WHERE omitted — dangerous, shown as a cautionary example): `UPDATE Customers SET ContactName='Juan';`. [S1]

## ⚖️ 모순 및 업데이트 (Contradictions & updates)
소스에서 모순되는 정보는 발견되지 않음. WHERE 생략의 위험성이 소스 내에서 두 차례 강조됨. [S1]

## 🛠️ 적용 사례 (Applied in summary)
현재 발견된 실제 적용 사례가 없습니다 — 프로덕션에서 UPDATE 실행 전 WHERE 조건을 SELECT로 먼저 검증하는 습관이 소스의 경고에서 자연스럽게 도출된다. [S1]

## 💻 코드 패턴 (Code patterns)
Update one record (SQL):
```sql
UPDATE Customers
SET ContactName = 'Alfred Schmidt', City= 'Frankfurt'
WHERE CustomerID = 1;
```
Update matching multiple records (SQL):
```sql
UPDATE Customers
SET ContactName='Juan'
WHERE Country='Mexico';
```

## ✅ 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 Delete]], [[SQL Insert Into]]
- **참조 맥락:** CRUD의 Update 축 — WHERE 절 누락 위험을 항상 함께 기억해야 한다.

## 📚 출처 (Sources)
- [S1] W3Schools — SQL UPDATE Statement — https://www.w3schools.com/sql/sql_update.asp

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