what is the best site for practicing excercies with solutions for sql ???

Answer 1

w3house.com
it may not be the best but you can practise.

Answer 2

tanq @andrei

Answer 3

you go and see a lesson. search an example an click "Try it" or smt like that and then you can code in the new tab

Answer 4

Khanacademy I THINK is good.