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A common table expression, or CTE, (in SQL) is a temporary named result set, derived from a simple query and defined within the execution scope of a SELECT, INSERT, UPDATE, or DELETE statement. CTEs can be thought of as alternatives to derived tables ( subquery ), views , and inline user-defined functions.
Since 1999 the SQL standard allows WITH clauses for subqueries, i.e. named subqueries, usually called common table expressions (also called subquery factoring). CTEs can also be recursive by referring to themselves; the resulting mechanism allows tree or graph traversals (when represented as relations), and more generally fixpoint computations.
This list includes SQL reserved words – aka SQL reserved keywords, [1] [2] as the SQL:2023 specifies and some RDBMSs have added. Reserved words in SQL and related products In SQL:2023 [ 3 ]
SELECT list is the list of columns or SQL expressions to be returned by the query. This is approximately the relational algebra projection operation. AS optionally provides an alias for each column or expression in the SELECT list. This is the relational algebra rename operation. FROM specifies from which table to get the data. [3]
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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 ...
Salman "Sal" Amin Khan (born October 11, 1976) is an American educator and the founder of Khan Academy, a free online non-profit educational platform with which he has produced over 6,500 video lessons teaching a wide spectrum of academic subjects, originally focusing on mathematics and science. [1]
The Table<T> encapsulates the data in the table, and implements the IQueryable<T> interface, so that the expression tree is created, which the LINQ to SQL provider handles. It converts the query into T-SQL and retrieves the result set from the database server. Since the processing happens at the database server, local methods, which are not ...