---
id: php-mysql-select-where
title: "PHP MySQL Select Where"
category: "Programming_Language"
status: "draft"
verification_status: "conceptual"
canonical_id: ""
aliases: ["WHERE clause", "PHP MySQL 필터링"]
duplicate_of: ""
source_trust_level: "B"
confidence_score: 0.89
created_at: 2026-07-04
updated_at: 2026-07-04
review_reason: ""
merge_history: []
tags: ["php", "programming", "w3schools", "mysql", "where"]
raw_sources: ["https://www.w3schools.com/php/php_mysql_select_where.asp"]
applied_in: []
github_commit: ""
---

# [[PHP MySQL Select Where]]

## 🎯 한 줄 통찰 (One-line insight)
This chapter reuses the EXACT same PHP structure as the plain SELECT chapter — only the SQL string itself changes (`... WHERE lastname='Doe'` appended) — demonstrating that filtering logic lives entirely in the SQL layer, with zero changes needed to the PHP fetch/loop code around it. [S1]

## 🧠 핵심 개념 (Core concepts)
- **`WHERE column operator value`** — filters records matching a condition. [S1]
- **Same PHP wrapper as plain SELECT** — connection, `query()`, `num_rows`/`rowCount()` check, `fetch_assoc()`/`fetch()` loop are all identical; only the SQL string differs. [S1]

## 📖 세부 내용 (Details)
- Filtered select: `$sql = "SELECT id, firstname, lastname FROM MyGuests WHERE lastname='Doe'"; $result = $conn->query($sql); if ($result->num_rows > 0) { while($row = $result->fetch_assoc()) { echo "id: " . $row["id"]. " - Name: " . $row["firstname"]. " " . $row["lastname"]. "<br>"; } }`. [S1]

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

## 🛠️ 적용 사례 (Applied in summary)
현재 발견된 실제 적용 사례가 없습니다 — lastname='Doe' 조건으로 특정 게스트만 조회하는 것이 필터링의 대표 실전 사례다. [S1]

## 💻 코드 패턴 (Code patterns)
Filtering results with WHERE, same PHP structure as plain SELECT (PHP/MySQLi):
```php
$sql = "SELECT id, firstname, lastname FROM MyGuests WHERE lastname='Doe'";
$result = $conn->query($sql);
if ($result->num_rows > 0) {
    while ($row = $result->fetch_assoc()) {
        echo "id: " . $row["id"] . " - Name: " . $row["firstname"] . " " . $row["lastname"] . "<br>";
    }
}
```

## ✅ 검증 상태 및 신뢰도
- **상태:** draft
- **검증 단계:** conceptual
- **출처 신뢰도:** B (W3Schools — widely used educational reference, not a primary standards body)
- **신뢰 점수:** 0.89
- **중복 검사 결과:** 신규 생성 (New discovery)

## 🔗 지식 그래프 (Knowledge Graph)
- **상위/루트:** [[PHP Tutorial]]
- **관련 개념:** [[PHP MySQL Select]], [[PHP MySQL Select Order By]]
- **참조 맥락:** WHERE 조건 필터링 — ORDER BY 정렬(Select Order By) 챕터로 이어짐.

## 📚 출처 (Sources)
- [S1] W3Schools — PHP MySQL The WHERE Clause — https://www.w3schools.com/php/php_mysql_select_where.asp

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