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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 family is something like a "view" on a number of tables. It can also be seen as a map of tables. Benefits It is useful when making a data model to have some kind of a view on a number of tables. Using a super column family is something similar to that in distributed data stores. There are, however, no "joins" between the "tables", as data stores like Apache Cassandra are non-relational. Sorting and querying There is no way to sort super columns after they have been inserted, nor to query an arbitrary query in distributed data stores. Super columns are sorted when they are added to the column family, and it is also possible to use a different sorting attribute for the contained columns of a super column. Similar to the standard column fa ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Super Column Family (data Store)
A super column family is a NoSQL (concept), NoSQL object that contains column families. It is a tuple (pair) that consists of a attribute–value pair, key–value pair, where the key is mapped to a value that are column families. In analogy with relational databases, a super column family is something like a "view" on a number of tables. It can also be seen as a map of tables. Benefits It is useful when making a data model to have some kind of a View (database), view on a number of Table (database), tables. Using a super column family is something similar to that in distributed data stores. There are, however, no "Join (database), joins" between the "tables", as data stores like Apache Cassandra are non-relational. Sorting and querying There is no way to sort super columns after they have been inserted, nor to Query language, query an arbitrary query in distributed data stores. Super columns are sorted when they are added to the column family, and it is also possible to use a di ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
NoSQL (concept)
A NoSQL (originally referring to "non- SQL" or "non-relational") database provides a mechanism for storage and retrieval of data that is modeled in means other than the tabular relations used in relational databases. Such databases have existed since the late 1960s, but the name "NoSQL" was only coined in the early 21st century, triggered by the needs of Web 2.0 companies. NoSQL databases are increasingly used in big data and real-time web applications. NoSQL systems are also sometimes called Not only SQL to emphasize that they may support SQL-like query languages or sit alongside SQL databases in polyglot-persistent architectures. Motivations for this approach include simplicity of design, simpler "horizontal" scaling to clusters of machines (which is a problem for relational databases), finer control over availability and limiting the object-relational impedance mismatch. The data structures used by NoSQL databases (e.g. key–value pair, wide column, graph, or docume ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tuple
In mathematics, a tuple is a finite ordered list (sequence) of elements. An -tuple is a sequence (or ordered list) of elements, where is a non-negative integer. There is only one 0-tuple, referred to as ''the empty tuple''. An -tuple is defined inductively using the construction of an ordered pair. Mathematicians usually write tuples by listing the elements within parentheses "" and separated by a comma and a space; for example, denotes a 5-tuple. Sometimes other symbols are used to surround the elements, such as square brackets "nbsp; or angle brackets "⟨ ⟩". Braces "" are used to specify arrays in some programming languages but not in mathematical expressions, as they are the standard notation for sets. The term ''tuple'' can often occur when discussing other mathematical objects, such as vectors. In computer science, tuples come in many forms. Most typed functional programming languages implement tuples directly as product types, tightly associated with algebr ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
View (database)
In a database, a view is the result set of a ''stored'' query on the data, which the database users can query just as they would in a persistent database collection object. This pre-established query command is kept in the database dictionary. Unlike ordinary ''base tables'' in a relational database, a view does not form part of the physical schema: as a result set, it is a virtual table computed or collated dynamically from data in the database when access to that view is requested. Changes applied to the data in a relevant ''underlying table'' are reflected in the data shown in subsequent invocations of the view. In some NoSQL databases, views are the only way to query data. Views can provide advantages over tables: * Views can represent a subset of the data contained in a table. Consequently, a view can limit the degree of exposure of the underlying tables to the outer world: a given user may have permission to query the view, while denied access to the rest of the base table. * ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Table (database)
A table is a collection of related data held in a table format within a database. It consists 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 columns (identifiable by name) and horizontal rows, the cell being the unit where a row and column intersect. A table has a specified number of columns, but can have any number of rows. Each row is identified by one or more values appearing in a particular column subset. A specific choice of columns which uniquely identify rows is called the primary key. "Table" is another term for "relation"; although there is the difference in that a table is usually a multiset (bag) of rows where a relation is a set and does not allow duplicates. Besides the actual data rows, tables generally have associated with them some metadata, such as constraints on the table or on the values within particular columns. The data in a table does not have to be physic ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Distributed Data Store
A distributed data store is a computer network where information is stored on more than one node, often in a replicated fashion. It is usually specifically used to refer to either a distributed database where users store information on a ''number of nodes'', or a computer network in which users store information on a ''number of peer network nodes''. Distributed databases Distributed databases are usually non-relational databases that enable a quick access to data over a large number of nodes. Some distributed databases expose rich query abilities while others are limited to a key-value store semantics. Examples of limited distributed databases are Google's Bigtable, which is much more than a distributed file system or a peer-to-peer network, Amazon's Dynamo and Microsoft Azure Storage. As the ability of arbitrary querying is not as important as the availability, designers of distributed data stores have increased the latter at an expense of consistency. But the high-speed r ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Join (database)
A join clause in SQL – corresponding to a Join (relational algebra), join operation in relational algebra – combines column (database), columns from one or more table (database), tables into a new table. Informally, a join stitches two tables and puts on the same row records with matching fields : INNER, LEFT OUTER, RIGHT OUTER, FULL OUTER and CROSS. Example tables To explain join types, the rest of this article uses the following tables: Department.DepartmentID is the primary key of the Department table, whereas Employee.DepartmentID is a foreign key. Note that in Employee, "Williams" has not yet been assigned to a department. Also, no employees have been assigned to the "Marketing" department. This is the SQL statement to create the above tables: CREATE TABLE department( DepartmentID INT PRIMARY KEY NOT NULL, DepartmentName VARCHAR(20) ); CREATE TABLE employee ( LastName VARCHAR(20), DepartmentID INT REFERENCES department(DepartmentID) ); INSERT INT ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Apache Cassandra
Cassandra is a free and open-source, distributed, wide-column store, NoSQL database management system designed to handle large amounts of data across many commodity servers, providing high availability with no single point of failure. Cassandra offers support for clusters spanning multiple datacenters, with asynchronous masterless replication allowing low latency operations for all clients. Cassandra was designed to implement a combination of Amazon's Dynamo distributed storage and replication techniques combined with Google's Bigtable data and storage engine model. History Avinash Lakshman, one of the authors of Amazon's Dynamo, and Prashant Malik initially developed Cassandra at Facebook to power the Facebook inbox search feature. Facebook released Cassandra as an open-source project on Google code in July 2008. In March 2009, it became an Apache Incubator project. On February 17, 2010, it graduated to a top-level project. Facebook developers named their database afte ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Query Language
Query languages, data query languages or database query languages (DQL) are computer languages used to make queries in databases and information systems. A well known example is the Structured Query Language (SQL). Types Broadly, query languages can be classified according to whether they are database query languages or information retrieval query languages. The difference is that a database query language attempts to give factual answers to factual questions, while an information retrieval query language attempts to find documents containing information that is relevant to an area of inquiry. Other types of query languages include: * Full-text. The simplest query language is treating all terms as bag of words that are to be matched with the postings in the inverted index and where subsequently ranking models are applied to retrieve the most relevant documents. Only tokens are defined in the CFG. Web search engines often use this approach. * Boolean. A query language that also s ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Column (data Store)
A column of a distributed data store is a NoSQL object of the lowest level in a keyspace. It is a tuple (a key–value pair) consisting of three elements: * Unique name: Used to reference the column * Value: The content of the column. It can have different types, like AsciiType, LongType, TimeUUIDType, UTF8Type among others. * Timestamp: The system timestamp used to determine the valid content. Usage A column is used as a store for the value and has a timestamp that is used to differentiate the valid content from stale ones. According to the CAP theorem, distributed data stores cannot guarantee consistency, as availability and partition tolerance are more important issues. Therefore, the data store or the application programmer will use the timestamp to find out which of the stored values in the backup nodes are up-to-date. Some data stores, like Riak, may use the more sophisticated vector clock instead of the timestamp to resolve stale information. Differences from a relatio ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Standard Column Family
The standard column family is a NoSQL (concept), NoSQL object that contains Column (data store), columns of related data. It is a tuple (pair) that consists of a attribute–value pair, key–value pair, where the key is mapped to a value that is a set of columns. In analogy with relational databases, a standard column family is as a "table", each key–value pair being a "row". Each column is a tuple (triplet (other), triplet) consisting of a column name, a value, and a timestamp. In a Relational database, relational database table, this data would be grouped together within a table with other non-related data. Standard column families are column containers sorted by their names can be referenced and sorted by their row key. Benefits Accessing the data in a Distributed computing, distributed data store would be expensive (time-consuming), if it would be saved in form of a table. It would also be inefficient to read all column families that would make up a row in a relati ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
