Recieving and sending data from and to database in attendance system

I'm designing an RFID attendance system,in which I'm trying to receive ID number from database and then compare that number with card number using arduino.After this i want to write in database and then fetch mobile number from database. Need your help. Thanks in advance.

I'm trying to receive ID number from database

Receive and send how? Serial, WiFi, Ethernet, Bluetooth, smoke signals? What database?

What have you tried?

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