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mssql_Study/join (cartesian).sql

31 lines
665 B

USE Study
GO
SELECT * FROM EMPLOYEE
SELECT * FROM DEPARTMENT
-- Cartesian product: ¸ðµç Æ©ÇÃ½Ö »ý¼º (same as Cross join)
SELECT * FROM EMPLOYEE, DEPARTMENT
select * from EMPLOYEE
select * from SALGRADE
-- Theta join
SELECT ENAME, GRADE
FROM EMPLOYEE, SALGRADE
WHERE LOWSAL <= SALARY AND SALARY <= HIGHSAL
SELECT ENAME, GRADE
FROM EMPLOYEE, SALGRADE
WHERE SALARY BETWEEN LOWSAL AND HIGHSAL
-- Self join
SELECT E.ENAME AS ENAME, M.ENAME AS MANAGER
FROM EMPLOYEE AS E, EMPLOYEE AS M
WHERE E.MANAGER = M.ENO
-- Mulitple join
SELECT ENAME, GRADE, DNAME
FROM EMPLOYEE, SALGRADE, DEPARTMENT
WHERE SALARY BETWEEN LOWSAL AND HIGHSAL
AND EMPLOYEE.DNO = DEPARTMENT.DNO