Blockchains are here for more than tenfifteen years and currently, we are adopting the blockchain techniques in databases, and vice-versa. Example, A typical blockchain data structures, such as cryptographically-linked blocks and Merkle trees, have been interspersed. Into verifiable databases. On the other hand, database techniques, such as sharding and concurrency control, have been interspersed. Into blockchains. In this paper, I am looking at systems that combine both blockchain and database techniques. I classify these systems into three types and that is given below (1) Permissioned Blockchains, (2) Hybrid Blockchain Database Systems, (3) Ledger Databases. I also present their anatomy, including the features, techniques, and design choices, by analyzing a few representative systems. In the end, I highlight their challenges and discuss research directions