A column family is a
database object
A database object is a structure for storing, Database administrator, managing and presenting application- or user-specific data in a database. Depending on the database management system (DBMS), many different types of database objects can exist. ...
that contains columns of related data. It is a
tuple
In mathematics, a tuple is a finite sequence or ''ordered list'' of numbers or, more generally, mathematical objects, which are called the ''elements'' of the tuple. An -tuple is a tuple of elements, where is a non-negative integer. There is o ...
(pair) that consists of a
key–value pair, where the key is mapped to a value that is a set of columns. In analogy with relational databases, a column family is as a "table", each key-value pair being a "row". Each column is a
tuple
In mathematics, a tuple is a finite sequence or ''ordered list'' of numbers or, more generally, mathematical objects, which are called the ''elements'' of the tuple. An -tuple is a tuple of elements, where is a non-negative integer. There is o ...
(
triplet) consisting of a column name, a value, and a
timestamp
A timestamp is a sequence of characters or encoded information identifying when a certain event occurred, usually giving date and time of day, sometimes accurate to a small fraction of a second. Timestamps do not have to be based on some absolu ...
. In a
relational database table
In a database, a table is a collection of related data organized in table format; consisting of columns and rows.
In relational databases, and flat file databases, a ''table'' is a set of data elements (values) using a model of vertical colum ...
, this data would be grouped together within a table with other non-related data.
Two types of column families exist:
*
Standard column family
The standard column family is a NoSQL object that contains columns of related data. It is a tuple (pair) that consists of a key–value pair, where the key is mapped to a value that is a set of columns. In analogy with relational databases, a stan ...
: contains only columns
*
Super column family
A super column family is a NoSQL object that contains column families. It is a tuple (pair) that consists of a key–value pair, where the key is mapped to a value that are column families. In analogy with relational databases, a super column fami ...
: contains a map of
super column
A super column is a tuple (a pair) with a binary super column name and a value that maps it to many columns. They consist of a key–value pairs, where the values are columns. Theoretically speaking, super columns are ( sorted) associative array o ...
s
See also
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Keyspace (NoSQL)
A keyspace (or key space) in a NoSQL data store is an object that holds together all column families of a design. It is the outermost grouping of the data in the data store. It resembles the schema concept in Relational database management system ...
References
{{reflist
External links
The Apache Cassandra data model Distributed data stores
NoSQL