Blockchain strives to eliminate the need for middlemen by building trust between business parties, automating certain transaction processes, securing transaction data, and reducing costs across the board by creating an immutable ledger or log of transactions or data. Blockchain can simplify the way business is conducted, but it is not a replacement for the database systems in place today.
A database is a system to store data, but a blockchain is a ledger to record and log movements. Unlike a traditional database, on a blockchain each participant maintains, calculates, and updates new entries into the database, and all nodes work together to ensure they reach the same conclusions. This provides in-built security for the network without requiring the access and permissions required by a central administrator in charge of securing a database.