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To further illustrate, imagine a relational model with two tables: a people table (which has a person_id and person_name column) and a friend table (with friend_id and person_id, which is a foreign key from the people table). In this case, searching for all of Jack's friends would result in the following SQL query.
The RDF model has been standardized by W3C in a number of specifications. The Property Graph model, on the other hand, has a multitude of implementations in graph databases, graph algorithms, and graph processing facilities. However, a common, standardized query language for property graphs (like SQL for relational database systems) is missing.
The nested set model is a technique for representing nested set collections (also known as trees or hierarchies) in relational databases. It is based on Nested Intervals, that "are immune to hierarchy reorganization problem, and allow answering ancestor path hierarchical queries algorithmically — without accessing the stored hierarchy relation".
The table above (even if some more columns are added) maintains one line per country for narrower browser and screen widths. So it is therefore more readable and scannable in long country tables. The table format below can greatly increase in number of lines, and require more vertical scrolling, especially if more columns are added.
Python has built-in set and frozenset types since 2.4, and since Python 3.0 and 2.7, supports non-empty set literals using a curly-bracket syntax, e.g.: {x, y, z}; empty sets must be created using set(), because Python uses {} to represent the empty dictionary.
The Size property is an integer that can be read (get) and written (set). Similarly, the Name property is a string that can also be read and modified, but its value is stored in a separate (private) class variable _name. Omitting the set operation in a property definition makes the property read-only, while omitting the get operation makes it ...
Functions that get executed before or after specific operations (like on a document insertion for example) that can either alter the operation or cancel it. Triggers are only executed on request. User-defined functions (UDF). Functions that can be called from and augment the SQL query language making up for limited SQL features.
Jinja is a web template engine for the Python programming language. It was created by Armin Ronacher and is licensed under a BSD License. Jinja is similar to the Django template engine, but provides Python-like expressions while ensuring that the templates are evaluated in a sandbox. It is a text-based template language and thus can be used to ...