💡 Alias
테이블의 열에 별칭을 지정하는데 사용하며, 쿼리가 살아있는 동안에만 적용된다.
/* 컬럼 alias */
SELECT colemn_name AS alias_name
FROM table_name;/* 테이블 alias */
SELECT column_name(s)
FROM table_name AS alias_name;Sample Table
Customers
| CustomerID | CustomerName | ContactName | Address | City | PostalCode | Country |
|---|---|---|---|---|---|---|
| 2 | Ana Trujillo Emparedados y helados | Ana Trujillo | Avda. de la Constitución 2222 | México D.F. | 05021 | Mexico |
| 3 | Antonio Moreno Taquería | Antonio Moreno | Mataderos 2312 | México D.F. | 05023 | Mexico |
| 4 | Around the Horn | Thomas Hardy | 120 Hanover Sq. | London | WA1 1DP | UK |
Orders
| OrderID | CustomerID | EmployeeID | OrderDate | ShipperID |
|---|---|---|---|---|
| 10354 | 58 | 8 | 1996-11-14 | 3 |
| 10355 | 4 | 6 | 1996-11-15 | 1 |
| 10356 | 86 | 6 | 1996-11-18 | 2 |
예시
CustomerId와 CustomerName 컬럼에 각각 하나씩 별칭 생성
SELECT CustomerID AS ID, CUstomerName AS Customer
FROM Customers;
별칭에 공백이 포함된 경우 " " 또는 [ ] 필요
SELECT CustomerID AS ID, CUstomerName AS [Customer Person]
FROM Customers;
4개의 컬럼을 묶어서 하나의 Address 별칭으로 생성
SELECT CustomerName, Address + ', ' + PostalCode + ' ' + City + ', ' Country AS Address
FROM customers;위의 예시의 Mysql 사용법
SELECT CustomerName, CONCAT(Address,', ',PostalCode,', ',City,',',Country) AS Address
FROM Customers
CustomerID가 4 (Around the Horn)인 고객의 모든 주문을 선택.
Order = o , Customers = c 별칭을 사용
별칭 미사용 예시
SELECT Orders.OrderID, Orders.OrderDate, Customers,CustomerName
FROM Customers, Orders
WHERE Customers.CustomerName = 'Around the Horn' AND
Customers.CustomerID = Orders.CustomerID;
별칭 사용 예시
SELECT o.OrderID, o.OrderDate, c.CustomerName
FROM Customers AS c, Orders AS o
WHERE c.CustomerName = 'Around the Horn' AND
c.CustomerID = o.CustomerID;