1-bob. Ma`lumotlar bazasining asosiy tushunchalari

SELECT surname, name, stipend kurs, (stipend*kurs)/2; FROM Student

WHERE kurs = 4 AND stipend >0

Joylashtirilgan so`rovlar

Misol. Joylashtirilgan so`rov:

SELECT name FROM users WHERE id_user IN (SELECT id_author FROM topics

WHERE topic_name='велосипедлар');

Misol. Xuddi shu so`rov:

SELECT name FROM users

WHERE id_user = (SELECT id_author FROM topics

WHERE topic_name='велосипедлар');

Moslashtirilgan so`rovda tashqi so`rov xar bir satri uchun ostki so`rov bajariladi

Misol:
SELECT *
FROM Customers outer
WHERE 10/03/1990 IN ( SELECT odate
FROM Orders inner
WHERE outer.cnum = inner.cnum );
Shu misol:
SELECT *
FROM Customers first, Orders second WHERE first.cnum = second.cnum AND second.odate = 10/03/1990; Misol.Tashqi so’rovdan foydalanish.
SELECT *
FROM Orders outer
WHERE amt > ( SELECT AVG amt
FROM Orders inter
WHERE inner.cnum = outer.cnum );


SQL da almashtirish funksiyalari bilan ishlash.

1. 
   LOWER ()- berilgan satrni kichik harflarga almashtirib beradi.
   
2. 
   UPPER () – kichik harflarni kata harflarga almashtirib beradi.
   
3. 
   INIT CAP ()- satrdagi har bir so’z unlikni 1-harfini bosh harf qilib beradi.
   

Maslan, ularga quyidagi misolni ko’ramiz. SELECT LOWER (surname), UPPER (name) FROM Student