Wide Column / Column Family NoSQL Database

Wide Column / Column Family Database

Wide column / column family databases are NoSQL databases that store data in records with an ability to hold very large numbers of dynamic columns. Columns can contain null values and data with different data types. In addition, data is stored in cells grouped in columns of data rather than as rows of data. Columns are logically grouped into column families. Column families can contain a virtually unlimited number of columns that can be created at run-time or while defining the schema. And column families are groups of similar data that is usually accessed together. Additionally, column families can be grouped together as super column families.

The basis of the architecture of wide column / column family databases is that data is stored in columns instead of rows as in a conventional relational database management system (RDBMS). And the names and format of the columns can vary from row to row in the same table. Subsequently, a wide column database can be interpreted as a two-dimensional key-value.  Wide column databases do often support the notion of column families that are stored separately. However, each such column family typically contains multiple columns that are used together, like traditional RDBMS tables. Within a given column family, all data is stored in a row-by-row fashion, such that the columns for a given row are stored together, rather than each column being stored separately.

Since wide column / column family databases do not utilize table joins that are common in traditional RDMS, they tend to scale and perform well even with massive amounts of included data.  And databases with billions of rows and hundreds or thousands of columns are common.  For example, a geographic information systems (GIS) like Google Earth may a row ID for every longitude position on the planet and a column for every latitude position.  Thus, if one database contains data on every square mile on Earth, there could be thousand of rows and thousands of columns in the database. And most of the columns in the database will have no value, meaning that the database is both large and sparsely populated.