Why are there so many databases _ MySQL

Why are there so many databases bitsCN.com?

Previously, Paul Graham showed us an interesting way to compare various programming languages: explaining what problems various programming languages are used to solve. I found that this method is also useful in databases:

Oracle: We need enterprise-level databases.

MySQL: Oracle is not open source.

PostgreSQL: MySQL does not have many functions.

SQLite: You can embed me anywhere. In this way, four databases are ready for use.

MongoDB: why do we use join and schema )?

CouchDB: why do we need collection )?

Redis: why do we need documentation?

Memcached: why are we using hard disks?

Neo4j: SQL lacks enough relationships.

Bigtable: MongoDB has poor web scalability.

Hbase: Bigtable is not open source.

Cassandra: Bigtable is not developed by Facebook.

Riak: Cassandra is not written in Erlang.

OrientDB: Let's put everything in the same database!

BitsCN.com