연산자 종류

• 연산자의 우선순위는 아래 순서대로이다.

1. 산술연산자

SELECT name, (Korean + English) AS sum FROM exam;

SELECT name, (Korean + English) / 2 AS average FROM exam
ORDER BY average DESC;

2. 비교연산자

SELECT id, name, English FROM exam
 WHERE English > 90;

SELECT id, name, Korean FROM exam
 WHERE name=’길동’;

3. IS NULL 연산자

SELECT * FROM book
WHERE price IS NOT NULL;

SELECT title + ‘은 가격미정” FROM book
WHERE price IS NULL;

4. LIKE 연산자 (와일드카드)

SELECT * FROM emp WHERE name LIKE ‘%혜%’;
SELECT * FROM emp WHERE name LIKE ‘혜_’;

5. IN 연산자

SELECT player FROM team
WHERE number IN (5, 10);
= (number = 5) OR (number = 10);

SELECT player FROM team
WHERE number NOT IN (1, 9);
= (number != 1) AND (number = !9);

6. BETWEEN 연산자

SELECT * FROM test
WHERE score BETWEEN 10 AND 100;

SELECT * FROM test
WHERE score NOT BETWEEN 90 AND 100;

7. 논리연산자

SELECT * FROM emp 
WHERE ( ( id%2 < 1 ) AND ( score >= 80 ) ); 

SELECT * FROM emp 
WHERE ( ( Korean >= 90 ) OR ( English >= 90 ) );

SELECT * FROM emp 
WHERE NOT ( ( Korean + English) > 150 );