[MySQL] AS

AS 

---

테이블의 컬럼에 이름을 붙인다.

AS를 생략해도 가능하다.

 

 

 

 

▶ 구문의 순서

FROM → WHERE → SELECT → ORDER BY
테이블선택 → 행 선택 → 열 선택 (추가 열)

 

 

 

 

 

▶ 예제

SELECT *, price * quantity AS amount FROM sample34;

+------+-------+----------+--------+
| no   | price | quantity | amount |
+------+-------+----------+--------+
|    1 |   100 |       10 |   1000 |
|    2 |   230 |       24 |   5520 |
|    3 |  1980 |        1 |   1980 |
+------+-------+----------+--------+

SELECT *, price * quantity amount FROM sample34;
+------+-------+----------+--------+
| no   | price | quantity | amount |
+------+-------+----------+--------+
|    1 |   100 |       10 |   1000 |
|    2 |   230 |       24 |   5520 |
|    3 |  1980 |        1 |   1980 |
+------+-------+----------+--------+

SELECT price * quantity AS '1000' FROM sample34;
+------+
| 1000 |
+------+
| 1000 |
| 5520 |
| 1980 |
+------+

SELECT *, price * quantity AS amount FROM sample34
WHERE price * quantity >= 2000;
    
+------+-------+----------+--------+
| no   | price | quantity | amount |
+------+-------+----------+--------+
|    2 |   230 |       24 |   5520 |
+------+-------+----------+--------+

SELECT *, price * quantity AS amount FROM sample34
ORDER BY price * quantity DESC;
+------+-------+----------+--------+
| no   | price | quantity | amount |
+------+-------+----------+--------+
|    2 |   230 |       24 |   5520 |
|    3 |  1980 |        1 |   1980 |
|    1 |   100 |       10 |   1000 |
+------+-------+----------+--------+

 

 

 

 

 

 

 

▶ 에러코드 예시

-- ERROR CODE
SELECT *, price * quantity AS amount FROM sample34 WHERE amount >= 2000;


-- Correction CODE
SELECT *, price * quantity AS amount FROM sample34 WHERE price * quantity >= 2000;