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2. SQL syntax - Wikipedia

   en.wikipedia.org/wiki/SQL_syntax

   SQL includes operators and functions for calculating values on stored values. SQL allows the use of expressions in the select list to project data, as in the following example, which returns a list of books that cost more than 100.00 with an additional sales_tax column containing a sales tax figure calculated at 6% of the price.

3. SQL - Wikipedia

   en.wikipedia.org/wiki/SQL

   SQL was initially developed at IBM by Donald D. Chamberlin and Raymond F. Boyce after learning about the relational model from Edgar F. Codd [12] in the early 1970s. [13] This version, initially called SEQUEL (Structured English Query Language), was designed to manipulate and retrieve data stored in IBM's original quasirelational database management system, System R, which a group at IBM San ...

4. Query by Example - Wikipedia

   en.wikipedia.org/wiki/Query_by_Example

   Example of QBE query with joins, designed in Borland's Paradox database. 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]

5. Join (SQL) - Wikipedia

   en.wikipedia.org/wiki/Join_(SQL)

   Conversely, an inner join can result in disastrously slow performance or even a server crash when used in a large volume query in combination with database functions in an SQL Where clause. [2] [3] [4] A function in an SQL Where clause can result in the database ignoring relatively compact table indexes. The database may read and inner join the ...

6. Programming paradigm - Wikipedia

   en.wikipedia.org/wiki/Programming_paradigm

   Given a database or a set of rules, the computer tries to find a solution matching all the desired properties. An archetype of a declarative language is the fourth generation language SQL, and the family of functional languages and logic programming. Functional programming is a subset of declarative programming.

7. Correlated subquery - Wikipedia

   en.wikipedia.org/wiki/Correlated_subquery

   In a SQL database query, a correlated subquery (also known as a synchronized subquery) is a subquery (a query nested inside another query) that uses values from the outer query. This can have major impact on performance because the correlated subquery might get recomputed every time for each row of the outer query is processed.

8. Set operations (SQL) - Wikipedia

   en.wikipedia.org/wiki/Set_operations_(SQL)

   Set operations in SQL is a type of operations which allow the results of multiple queries to be combined into a single result set. [ 1 ] Set operators in SQL include UNION , INTERSECT , and EXCEPT , which mathematically correspond to the concepts of union , intersection and set difference .

9. Database normalization - Wikipedia

   en.wikipedia.org/wiki/Database_normalization

   A basic objective of the first normal form defined by Codd in 1970 was to permit data to be queried and manipulated using a "universal data sub-language" grounded in first-order logic. [1] An example of such a language is SQL , though it is one that Codd regarded as seriously flawed.