---
id: php-mysql-update
title: "PHP MySQL Update"
category: "Programming_Language"
status: "draft"
verification_status: "conceptual"
canonical_id: ""
aliases: ["UPDATE SET", "PHP MySQL 수정"]
duplicate_of: ""
source_trust_level: "B"
confidence_score: 0.88
created_at: 2026-07-04
updated_at: 2026-07-04
review_reason: ""
merge_history: []
tags: ["php", "programming", "w3schools", "mysql", "update"]
raw_sources: ["https://www.w3schools.com/php/php_mysql_update.asp"]
applied_in: []
github_commit: ""
---

# [[PHP MySQL Update]]

## 🎯 한 줄 통찰 (One-line insight)
`UPDATE` shares the exact same danger as `DELETE` — omitting `WHERE` updates ALL records in the table, not just none — meaning both destructive SQL operations (mass-delete and mass-overwrite) are gated behind the same single safety mechanism, the WHERE clause. [S1]

## 🧠 핵심 개념 (Core concepts)
- **`UPDATE table SET col=val WHERE condition`** — modifies matching records. [S1]
- **WHERE limits the blast radius** — omitting it updates EVERY record in the table (same risk pattern as DELETE). [S1]
- **Executed like DELETE/INSERT** — `$conn->query($sql)` (MySQLi OOP), `mysqli_query($conn, $sql)` (procedural), `$conn->exec($sql)` (PDO). [S1]

## 📖 세부 내용 (Details)
- Update by ID: `$sql = "UPDATE MyGuests SET lastname='Doe' WHERE id=2"; if ($conn->query($sql) === TRUE) { echo "Record updated successfully"; } else { echo "Error updating record: " . $conn->error; }`. [S1]
- Before/after table state: id=2's lastname changes from "Moe" to "Doe" after the update, all other rows/columns unchanged. [S1]

## ⚖️ 모순 및 업데이트 (Contradictions & updates)
- **WHERE 절 생략의 파괴적 결과**: DELETE와 마찬가지로 WHERE 절을 생략하면 테이블의 모든 레코드가 수정된다는 점이 동일하게 경고됨. [S1]

## 🛠️ 적용 사례 (Applied in summary)
현재 발견된 실제 적용 사례가 없습니다 — id=2 게스트의 성만 변경하는 것이 안전한 조건부 수정의 표준 패턴이다. [S1]

## 💻 코드 패턴 (Code patterns)
Updating a specific record, WHERE clause required (SQL/PHP):
```php
$sql = "UPDATE MyGuests SET lastname='Doe' WHERE id=2"; // WHERE prevents updating every row
if ($conn->query($sql) === TRUE) {
    echo "Record updated successfully";
}
```

## ✅ 검증 상태 및 신뢰도
- **상태:** draft
- **검증 단계:** conceptual
- **출처 신뢰도:** B (W3Schools — widely used educational reference, not a primary standards body)
- **신뢰 점수:** 0.88
- **중복 검사 결과:** 신규 생성 (New discovery)

## 🔗 지식 그래프 (Knowledge Graph)
- **상위/루트:** [[PHP Tutorial]]
- **관련 개념:** [[PHP MySQL Delete]], [[PHP MySQL Select Limit]]
- **참조 맥락:** 레코드 수정 — 결과 제한(Select Limit) 챕터로 이어짐.

## 📚 출처 (Sources)
- [S1] W3Schools — PHP MySQL Update Data — https://www.w3schools.com/php/php_mysql_update.asp

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