use HR
select ROUND (3.44,5)-- yuvarlama yapar
select ABS (-1234)-- mutlak değer alır
select POWER (3,4)-- ÜST değer alır
select avg (salary) as ortalama  from EMPLOYEES-- tüm satırları toplayıp satır sayısına böler 
select max (salary) as ortalama  from EMPLOYEES -- en yuksek bir tanesini getirir
select min (salary) as ortalama  from EMPLOYEES -- en düşük bir tanesini getirir

select FIRST_NAME,LAST_NAME, SALARY as MAASI  from EMPLOYEES -- en ADI SOYADI OLAN KİŞİ MAASI EN  yuksek bir tanesini getirir
WHERE SALARY =(SELECT MAX (SALARY) FROM EMPLOYEES)


SELECT RAND (7),(4)

SELECT AVG (SALARY) FROM EMPLOYEES

SELECT GETDATE()-- SİSTEM TARİHİNİ CEKER

SELECT LAST_NAME, DATEDIFF(YEAR, HIRE_DATE,GETDATE()) AS WEEKS  -- TARİH ARALIĞINDAKİLERİ GETİR
FROM EMPLOYEES
WHERE DEPARTMENT_ID=90

SELECT LAST_NAME, DATEPART(YEAR, HIRE_DATE) AS WEEKS  -- İŞE BAŞLAMA TARİHLERİ
FROM EMPLOYEES
WHERE DEPARTMENT_ID=90