What is the main difference between document stores and column stores?
The main difference is that document stores (e.g. MongoDB and CouchDB) allow arbitrarily complex documents, i.e. subdocuments within subdocuments, lists with documents, etc. whereas column stores (e.g. Cassandra and HBase) only allow a fixed format, e.g. strict one-level or two-level dictionaries.
What is the difference between key-value and document database?
The difference lies in the way the data is processed; in a key-value store, the data is considered to be inherently opaque to the database, whereas a document-oriented system relies on internal structure in the document in order to extract metadata that the database engine uses for further optimization.
Which is an example of a wide column store?
A good example is a Customer table. The columns hold values describing the Customer’s name, address, and contact information. All of this information is the same for each and every customer. A wide column database is one type of NoSQL database. Maybe this is a better image of four wide column databases.
How is data stored in a column store?
What a column store does is defined in its name. Instead of storing data in rows or records the data is stored in columns. That way, when you want to compute the average age you only have to read the data with age information into memory instead of all the data in each row.
How are wide column stores used in RDMS?
Most (if not all) Wide-column stores are indeed row-oriented stores in that every parts of a record are stored together. You can see that as a 2-dimensional key-value store. The first part of the key is used to distribute the data across servers, the second part of the key lets you quickly find the data on the target server.
Which is the best document store to use?
A popular document store you might have heard of is MongoDB. A wide column store is somewhere in between a document store and a relational DB. It still uses tables, rows, and columns like a relational DB, but the names and formats of the columns can be different for various rows in the same table.