digital signature implementation in c++

this will be my first question here...soo plzz kndly help me...am in urgent need of this!

so i have to develop a c++ code for implementation of digital signatures. i understand the basic concept of it...but am kind of a noob wen it comes to c++ coding...sopoo can someone pllzz tell me step by step procedure of how to develop a code for digitaly signing a databse and den a code for verifying that previously signed database. sooo far wat i have done is: 1. created a databse using microsoft sql server 2. have found a library only for hashin which contains hashing function(m facing a problem here . the function sha256() requires to pass the databse as an arguement i dnt know how to do dat soo plzz if u can guide me through dis also) 3. i ll be provided with a doungle containing my private key for signing of the document. preferably i ll be using rsa signing.

sooo this wat i did and know abt dis project of mine...

i request to person answering to be exclusive and xplain in detail to how to approch and code dis in c++ as i a dnt possess ant thorogh knowledge of dis topic thank you!