---
id: sql-injection
title: "SQL Injection"
category: "Database"
status: "draft"
verification_status: "conceptual"
canonical_id: ""
aliases: ["SQL 인젝션"]
duplicate_of: ""
source_trust_level: "B"
confidence_score: 0.87
created_at: 2026-07-04
updated_at: 2026-07-04
review_reason: ""
merge_history: []
tags: ["sql", "database", "w3schools", "security", "injection"]
raw_sources: ["https://www.w3schools.com/sql/sql_injection.asp"]
applied_in: []
github_commit: ""
---

# [[SQL Injection]]

## 🎯 한 줄 통찰 (One-line insight)
SQL injection exploits raw string concatenation of user input into a query — a tautology like `OR 1=1` or a batched `; DROP TABLE ...` can turn a single-row lookup into a full-table dump or destructive command. [S1]

## 🧠 핵심 개념 (Core concepts)
- **SQL injection** — a code injection technique where attackers insert malicious SQL into user-input fields to read, modify, or delete sensitive data. [S1]
- **Root cause** — building SQL strings by concatenating raw user input, e.g. `txtSQL = "SELECT * FROM Users WHERE UserId = " + txtUserId;`. [S1]
- **Tautology injection (`1=1`)** — input like `105 OR 1=1` makes the WHERE clause always true, returning every row. [S1]
- **Tautology injection (`""=""`)** — the same idea applied to string-quoted login fields (`" OR ""="`), bypassing username/password checks entirely. [S1]
- **Batched statement injection** — a semicolon lets an attacker append an entirely separate destructive statement, e.g. `UserId = 105; DROP TABLE Suppliers;`. [S1]

## 🧩 추출된 패턴 (Extracted patterns)
- **Never trust concatenated input** — every example in the source traces back to the same root cause: building a SQL string by directly concatenating unescaped, unvalidated user input. [S1]
- **The fix lives in the next two chapters** — the source explicitly defers the mitigation (SQL Parameters, SQL Prepared Statements) rather than covering it here. [S1]

## 📖 세부 내용 (Details)
- Vulnerable pattern: `txtUserId = getRequestString("UserId"); txtSQL = "SELECT * FROM Users WHERE UserId = " + txtUserId;`. [S1]
- Tautology exploit: input `105 OR 1=1` yields `SELECT * FROM Users WHERE UserId = 105 OR 1=1;`, returning ALL rows. [S1]
- Login bypass exploit: input `" OR ""="` on both fields yields `SELECT * FROM Users WHERE Name ="" or ""="" AND Pass ="" or ""=""`, which is always true. [S1]
- Batched destructive exploit: `SELECT * FROM Users WHERE UserId = 105; DROP TABLE Suppliers;`. [S1]

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

## 🛠️ 적용 사례 (Applied in summary)
현재 발견된 실제 적용 사례가 없습니다 — 다음 두 챕터(SQL Parameters, SQL Prepared Statements)가 이 문제의 실제 해결책을 제시한다. [S1]

## 💻 코드 패턴 (Code patterns)
Vulnerable string-concatenation pattern (illustrative, NOT recommended):
```
txtUserId = getRequestString("UserId");
txtSQL = "SELECT * FROM Users WHERE UserId = " + txtUserId;
```

## ✅ 검증 상태 및 신뢰도
- **상태:** draft
- **검증 단계:** conceptual
- **출처 신뢰도:** B (W3Schools — widely used educational reference, not a primary standards body)
- **신뢰 점수:** 0.87
- **중복 검사 결과:** 신규 생성 (New discovery)

## 🔗 지식 그래프 (Knowledge Graph)
- **상위/루트:** [[SQL Tutorial]]
- **관련 개념:** [[SQL Parameters]], [[SQL Prepared Statements]]
- **참조 맥락:** 사용자 입력을 다루는 모든 쿼리 작성 전 반드시 인지해야 할 보안 위협 — 해결책은 다음 두 챕터.

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

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