예시)
CREATE TABLE employee(
empno int NOT NULL,
empname varvhar(45) DEFAULT '사원',
salary int,
dno int,
CONSTRAINT UQ_empname UNIQUE(empname),
CONSTRAINT CH_salary CHECK(salary<6000000),
CONSTRAINT CH_dno CHECK(dno IN(1,2,3,4,5,6))
);
ALTER TABLE employee
ADD CONSTRAINT UQ_empname UNIQUE(EMPNAME);
ALTER TABLE employee
DROP INDEX UQ_empname;
CREATE TABLE Orders(
ID int NOT NULL,
OrderNumber int NOT NULL,
OrderDate date DEFAULT(CURRENT_DATE())
)
ALTER TABLE employee
ALTER title SET DEFAULT '사원';
ALTER TABLE employee
ALTER title DROP DEFAULT;
ALTER TABLE employee
ADD CONSTRAINT CH_salary CHECK(salary < 6000000);
ALTER TABLE employee
DROP CONSTRAINT CH_salary;
SELECT 속성명
FROM relation명
SELECT dno, AVG(salary) as avgsal, MAX(salary) as maxsal
FROM employee
GROUP BY dno
HAVING AVG(salary)>=2500000;
-> 그룹으로 나눈 것 중에서 salary의 평균이 2500000이상인 것만 출력
SELECT salary, title, empname
FROM employee
WHERE dno=2
ORDER BY salary;
SELECT *
FROM employee
LIMIT 3;