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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.
AutoHotkey: As the first character of continued line; any expression operators except ++ and --, and a comma or a period [7] Some form of line comment serves as line continuation. Turbo Assembler: \ m4: dnl; TeX: % Character position. Fortran 77: A non-comment line is a continuation of the prior non-comment line if any non-space character ...
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 ...
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 ]
If the character is not found most of these routines return an invalid index value – -1 where indexes are 0-based, 0 where they are 1-based – or some value to be interpreted as Boolean FALSE. This can be accomplished as a special case of #Find , with a string of one character; but it may be simpler or more efficient in many languages to ...
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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.
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.