The tools like crystal reports or xcelcius do not connect to the SAP DB directly. In case you have a standalone DB then maybe you can connect. The standard procedure is to connect your Crystal reports to SAP BO, which in turn connects to the SAP BW( or any) Application and you can read the data present in DB. You can also use the Universal builder tool to build your universe.
In case you have further doubts kindly raise your queries in BO forums. You will get better responses there.
if you want data from SAP BW from crystal reports it is possible through mdx query connection crystal reports but you can access this data through info cueb,dso's, multi providers, quires
And also you can directly get the data of sap r3 system(oltp) from crystal report using sap drivers that is advantage of crystal report it can access data from oltp system also