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  2. Database index - Wikipedia

    en.wikipedia.org/wiki/Database_index

    A bitmap index is a special kind of indexing that stores the bulk of its data as bit arrays (bitmaps) and answers most queries by performing bitwise logical operations on these bitmaps. The most commonly used indexes, such as B+ trees, are most efficient if the values they index do not repeat or repeat a small number of times. In contrast, the ...

  3. 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.

  4. Hierarchical and recursive queries in SQL - Wikipedia

    en.wikipedia.org/wiki/Hierarchical_and_recursive...

    In SQL:1999 a recursive (CTE) query may appear anywhere a query is allowed. It's possible, for example, to name the result using CREATE [ RECURSIVE ] VIEW . [ 16 ] Using a CTE inside an INSERT INTO , one can populate a table with data generated from a recursive query; random data generation is possible using this technique without using any ...

  5. Lookup table - Wikipedia

    en.wikipedia.org/wiki/Lookup_table

    One discrete problem that is expensive to solve on many computers is that of counting the number of bits that are set to 1 in a (binary) number, sometimes called the population function. For example, the decimal number "37" is "00100101" in binary, so it contains three bits that are set to binary "1". [7]: 282

  6. Zero-based numbering - Wikipedia

    en.wikipedia.org/wiki/Zero-based_numbering

    In mathematics, many sequences of numbers or of polynomials are indexed by nonnegative integers, for example, the Bernoulli numbers and the Bell numbers. In both mechanics and statistics , the zeroth moment is defined, representing total mass in the case of physical density , or total probability, i.e. one, for a probability distribution .

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    mail.aol.com

    Get AOL Mail for FREE! Manage your email like never before with travel, photo & document views. Personalize your inbox with themes & tabs. You've Got Mail!

  8. Expression index - Wikipedia

    en.wikipedia.org/wiki/Expression_index

    Within computing and computer science, an expression index, also known as a function based index, is a database index that is built on a generic expression, rather than one or more columns. This allows indexes to be defined for common query conditions that depend on data in a table, but are not actually stored in that table.

  9. Aggregate function - Wikipedia

    en.wikipedia.org/wiki/Aggregate_function

    The listagg function, as defined in the SQL:2016 standard [2] aggregates data from multiple rows into a single concatenated string. In the entity relationship diagram , aggregation is represented as seen in Figure 1 with a rectangle around the relationship and its entities to indicate that it is being treated as an aggregate entity.