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The Worldwide Protein Data Bank (wwPDB) is an organization that maintains the archive of macromolecular structure.Its mission is to maintain a single Protein Data Bank Archive of macromolecular structural data that is freely and publicly available to the global community.
Query by Example (QBE) is a database query language for relational databases. It was devised by Moshé M. Zloof at IBM Research during the mid-1970s, in parallel to the development of SQL . [ 1 ] It is the first graphical query language, using visual tables where the user would enter commands, example elements and conditions.
It can sometimes be useful to run queries against this database to extract information that is otherwise hard to find. For example: Articles with H.M.S. in their title that have not been edited for 12 months. Redirects with fewer than 20 incoming links that redirect to categories; All red links on pages within the scope of a particular WikiProject
The query evaluation, and thus query containment, is LOGCFL-complete and thus in polynomial time. [9] Acyclicity of conjunctive queries is a structural property of queries that is defined with respect to the query's hypergraph : [ 6 ] a conjunctive query is acyclic if and only if it has hypertree-width 1.
This example of the Pareto principle (or 80–20 rule) allows search engines to employ optimization techniques such as index or database partitioning, caching and pre-fetching. In addition, studies have been conducted into linguistically-oriented attributes that can recognize if a web query is navigational, informational or transactional. [14]
A query includes a list of columns to include in the final result, normally immediately following the SELECT keyword. An asterisk ("*") can be used to specify that the query should return all columns of all the queried tables. SELECT is the most complex statement in SQL, with optional keywords and clauses that include:
The above examples are a simple illustration of a basic relationship query. They condense the idea of relational models' query complexity that increases with the total amount of data. In comparison, a graph database query is easily able to sort through the relationship graph to present the results.
Correlated subqueries may appear elsewhere besides the WHERE clause; for example, this query uses a correlated subquery in the SELECT clause to print the entire list of employees alongside the average salary for each employee's department. Again, because the subquery is correlated with a column of the outer query, it must be re-executed for ...