About a song of movie

I had bought a soundtrack of the movie "Precious" about last week. I love a song that appeared in the movie trailer.


But it's odd, the song that I like didn't appear in the CD. Why? Because the song did not appear in the movie, so it couldn't be included in the soundtrack? This is unreasonable. I thought the movie trailer is also important.

Therefore, you should look for a album of the singer if tou want to hear the song you like.

There is the information of the song. ↓

Singer: Mary J blige

Song name: Destiny