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  2. Help:Sortable tables - Wikipedia

    en.wikipedia.org/wiki/Help:Sortable_tables

    As a result, multi-key sorting (sorting by primary, secondary, tertiary keys, etc.) can be achieved by sorting the least significant key first and the most significant key last. For example, to sort the table by the "Text" column and then by the "Numbers" column, you would first click on and sort by the "Numbers" column, the secondary key, and ...

  3. Sort-merge join - Wikipedia

    en.wikipedia.org/wiki/Sort-merge_join

    The sort-merge join (also known as merge join) is a join algorithm and is used in the implementation of a relational database management system.. The basic problem of a join algorithm is to find, for each distinct value of the join attribute, the set of tuples in each relation which display that value.

  4. Composite key - Wikipedia

    en.wikipedia.org/wiki/Composite_key

    In database design, a composite key is a candidate key that consists of two or more attributes, [1] [2] [3] (table columns) that together uniquely identify an entity occurrence (table row). A compound key is a composite key for which each attribute that makes up the key is a foreign key in its own right.

  5. Order by - Wikipedia

    en.wikipedia.org/wiki/Order_by

    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

  6. Database index - Wikipedia

    en.wikipedia.org/wiki/Database_index

    When multiple databases and multiple tables are joined, it is called a cluster (not to be confused with clustered index described previously). The records for the tables sharing the value of a cluster key shall be stored together in the same or nearby data blocks.

  7. SQL syntax - Wikipedia

    en.wikipedia.org/wiki/SQL_syntax

    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.

  8. First normal form - Wikipedia

    en.wikipedia.org/wiki/First_normal_form

    A table that lacks a unique key constraint. Such a table would be able to accommodate duplicate rows, in violation of condition 3. A view whose definition mandates that results be returned in a particular order, so that the row-ordering is an intrinsic and meaningful aspect of the view.

  9. Select (SQL) - Wikipedia

    en.wikipedia.org/wiki/Select_(SQL)

    Previous Page: sort the data in the reverse order, select only the first {rows} rows, where the {unique_key} is less than {first_val} (the value of the {unique_key} of the first row in the current page), and sort the result in the correct order