---
id: sql-aliases
title: "SQL Aliases"
category: "Database"
status: "draft"
verification_status: "conceptual"
canonical_id: ""
aliases: ["SQL Alias", "AS keyword", "SQL 별칭"]
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", "alias", "join"]
raw_sources: ["https://www.w3schools.com/sql/sql_alias.asp"]
applied_in: []
github_commit: ""
---

# [[SQL Aliases]]

## 🎯 한 줄 통찰 (One-line insight)
An alias, created with AS, gives a column or table a temporary, more readable name that exists only for the duration of the query — and becomes essential once tables are joined. [S1]

## 🧠 핵심 개념 (Core concepts)
- **Alias** — created with the `AS` keyword; makes a column name more readable; only exists for the duration of that query. [S1]
- **Column alias syntax** — `SELECT column_name AS alias_name FROM table_name;`. [S1]
- **Table alias syntax** — `SELECT column_name(s) FROM table_name AS alias_name;`. [S1]
- **Aliases with spaces** — wrap in square brackets `[My Great Products]` or double quotes `"My Great Products"` (support varies by DB system). [S1]
- **Concatenation alias** — combining multiple columns into one output column needs an alias to name the combined result. [S1]

## 🧩 추출된 패턴 (Extracted patterns)
- **Table alias for joins** — short aliases like `c` for customers and `o` for orders make multi-table JOIN queries shorter and more readable: `FROM customers AS c JOIN orders AS o ON c.customerID = o.customerID`. [S1]
- **Vendor-specific concatenation syntax** — the same "combine 4 address columns into one" intent needs different syntax per DB: `+` (SQL Server), `CONCAT()` (MySQL), `||` (Oracle). [S1]
- **When aliases matter most** — the source lists: multiple tables in a query, functions used in the query, long/unclear column names, and combined columns. [S1]

## 📖 세부 내용 (Details)
- Basic column alias: `SELECT CustomerID AS ID, CustomerName AS Customer FROM Customers;`. [S1]
- Alias with spaces (bracket form): `SELECT ProductName AS [My Great Products] FROM Products;`. [S1]
- Alias with spaces (quote form): `SELECT ProductName AS "My Great Products" FROM Products;`. [S1]
- Concatenated column alias (SQL Server): `SELECT CustomerName, Address + ', ' + PostalCode + ' ' + City + ', ' + Country AS Address FROM Customers;`. [S1]
- Same intent in MySQL: `SELECT CustomerName, CONCAT(Address,', ',PostalCode,', ',City,', ',Country) AS Address FROM Customers;`. [S1]
- Same intent in Oracle: `SELECT CustomerName, (Address || ', ' || PostalCode || ' ' || City || ', ' || Country) AS Address FROM Customers;`. [S1]
- Table alias: `SELECT * FROM Customers AS Persons;` and, for joins, `FROM customers AS c JOIN orders AS o ON c.customerID = o.customerID`. [S1]

## ⚖️ 모순 및 업데이트 (Contradictions & updates)
- **문자열 연결 문법이 DB마다 다름**: 동일한 "4개 컬럼 합치기" 요구가 SQL Server(`+`), MySQL(`CONCAT()`), Oracle(`||`)에서 각각 다른 연산자로 구현됨 — 표준 SQL이 아닌 방언별 차이. [S1]

## 🛠️ 적용 사례 (Applied in summary)
현재 발견된 실제 적용 사례가 없습니다 — 이후 JOIN 챕터 전체에서 테이블 별칭(c, o 등)이 관용적으로 재사용된다. [S1]

## 💻 코드 패턴 (Code patterns)
Column alias (SQL):
```sql
SELECT CustomerID AS ID, CustomerName AS Customer
FROM Customers;
```
Table alias for a join (SQL):
```sql
SELECT c.CustomerName, o.OrderID
FROM customers AS c
JOIN orders AS o ON c.customerID = o.customerID;
```

## ✅ 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 Select]], [[SQL Joins]], [[SQL Inner Join]]
- **참조 맥락:** 다중 테이블 JOIN 쿼리를 읽기 쉽게 만드는 표준 관용구 — 이후 모든 JOIN 챕터의 전제 지식.

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

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