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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]
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 .
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.
The sort criteria can be expressions, including column names, user-defined functions, arithmetic operations, or CASE expressions. The expressions are evaluated and the results are used for the sorting, i.e., the values stored in the column or the results of the function call. ORDER BY is the only way to sort the rows in the result set.
The relational algebra uses set union, set difference, and Cartesian product from set theory, and adds additional constraints to these operators to create new ones.. For set union and set difference, the two relations involved must be union-compatible—that is, the two relations must have the same set of attributes.
Players will select from the gift pool in an assigned order: Guests can draw straws to see who will go when, or the host can set an order prior to the event. Anything works, as long as people know ...
At least two dozen people are dead and more than 150,000 people have been forced from their homes. Speculation mounts over Trump's approach to Ukraine. With Trump set to take office in a week, his ...
Zeke Mayo scored 25 points, Hunter Dickinson had 15 points and 13 rebounds and No. 8 Kansas defeated Brown 87-53 on Sunday. Mayo hit two of his five 3-pointers on consecutive possessions to extend ...