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Relational algebra is a branch of mathematics that studies the manipulation and analysis of data in relational databases. It defines a set of operations, such as selection, projection, join, and union, that can be applied to relations or sets of tuples. Learn more about the concepts and notation of relational algebra on Wikipedia, including the rename operation that changes the attribute name ...
Select (SQL) The SQL SELECT statement returns a result set of rows, from one or more tables. [1] [2] A SELECT statement retrieves zero or more rows from one or more database tables or database views. In most applications, SELECT is the most commonly used data manipulation language (DML) command. As SQL is a declarative programming language ...
A derived table is the use of referencing an SQL subquery in a FROM clause. Essentially, the derived table is a subquery that can be selected from or joined to. The derived table functionality allows the user to reference the subquery as a table. The derived table is sometimes referred to as an inline view or a subselect.
The order of operations, that is, the order in which the operations in an expression are usually performed, results from a convention adopted throughout mathematics, science, technology and many computer programming languages. It is summarized as: [2] [5] Parentheses; Exponentiation; Multiplication and division; Addition and subtraction
Relation (database) Relation, tuple, and attribute represented as table, row, and column respectively. In database theory, a relation, as originally defined by E. F. Codd, [ 1] is a set of tuples (d 1 ,d 2 ,...,d n ), where each element d j is a member of D j, a data domain. Codd's original definition notwithstanding, and contrary to the usual ...
The following tables list the computational complexity of various algorithms for common mathematical operations . Here, complexity refers to the time complexity of performing computations on a multitape Turing machine. [ 1] See big O notation for an explanation of the notation used. Note: Due to the variety of multiplication algorithms, below ...
A foreign key is defined as an attribute or set of attributes in a relation whose values match a primary key in another relation. The syntax to add such a constraint to an existing table is defined in SQL:2003 as shown below. Omitting the column list in the REFERENCES clause implies that the foreign key shall reference the primary key of the ...
In computer science, a ternary operator is an operator that takes three arguments (or operands). [ 1] The arguments and result can be of different types. Many programming languages that use C-like syntax [ 4] feature a ternary operator, ?:, which defines a conditional expression. In some languages, this operator is referred to as the ...