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  2. Help:Basic table markup - Wikipedia

    en.wikipedia.org/wiki/Help:Basic_table_markup

    Name Markup Comments Table start {| It opens a table (and is required) Table caption |+ It adds a caption (and is optional, but recommended according to accessibility guidelines) Table row |-It adds a new row (and is optional for the first row) Header cell ! It adds a header cell, whose content can optionally be placed on a new line

  3. Apache Spark - Wikipedia

    en.wikipedia.org/wiki/Apache_Spark

    Spark Core is the foundation of the overall project. It provides distributed task dispatching, scheduling, and basic I/O functionalities, exposed through an application programming interface (for Java, Python, Scala, .NET [16] and R) centered on the RDD abstraction (the Java API is available for other JVM languages, but is also usable for some other non-JVM languages that can connect to the ...

  4. Name–value pair - Wikipedia

    en.wikipedia.org/wiki/Name–value_pair

    A name–value pair, also called an attribute–value pair, key–value pair, or field–value pair, is a fundamental data representation in computing systems and applications. Designers often desire an open-ended data structure that allows for future extension without modifying existing code or data.

  5. Identity column - Wikipedia

    en.wikipedia.org/wiki/Identity_column

    An identity column differs from a primary key in that its values are managed by the server and usually cannot be modified. In many cases an identity column is used as a primary key; however, this is not always the case. It is a common misconception that an identity column will enforce uniqueness; however, this is not the case. If you want to ...

  6. Anonymous recursion - Wikipedia

    en.wikipedia.org/wiki/Anonymous_recursion

    This creates a higher-order function, and passing this higher function itself allows anonymous recursion within the actual recursive function. This can be done purely anonymously by applying a fixed-point combinator to this higher order function. This is mainly of academic interest, particularly to show that the lambda calculus has recursion ...

  7. Primary key - Wikipedia

    en.wikipedia.org/wiki/Primary_key

    In the relational model of databases, a primary key is a designated attribute that can reliably identify and distinguish between each individual record in a table.The database creator can choose an existing unique attribute or combination of attributes from the table (a natural key) to act as its primary key, or create a new attribute containing a unique ID that exists solely for this purpose ...

  8. Foreign key - Wikipedia

    en.wikipedia.org/wiki/Foreign_key

    A foreign key is a set of attributes in a table that refers to the primary key of another table, linking these two tables. In the context of relational databases, a foreign key is subject to an inclusion dependency constraint that the tuples consisting of the foreign key attributes in one relation, R, must also exist in some other (not necessarily distinct) relation, S; furthermore that those ...

  9. Column family - Wikipedia

    en.wikipedia.org/wiki/Column_family

    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 column family is as a "table", each key-value pair being a "row". Each column is a tuple consisting of a column name, a value, and a timestamp.