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  2. Data cleansing - Wikipedia

    en.wikipedia.org/wiki/Data_cleansing

    Set-Membership constraints: The values for a column come from a set of discrete values or codes. For example, a person's sex may be Female, Male or Non-Binary. Foreign-key constraints: This is the more general case of set membership. The set of values in a column is defined in a column of another table that contains unique values.

  3. Selection sort - Wikipedia

    en.wikipedia.org/wiki/Selection_sort

    A bidirectional variant of selection sort (called double selection sort or sometimes cocktail sort due to its similarity to cocktail shaker sort) finds both the minimum and maximum values in the list in every pass. This requires three comparisons per two items (a pair of elements is compared, then the greater is compared to the maximum and the ...

  4. 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

  5. Sorting algorithm - Wikipedia

    en.wikipedia.org/wiki/Sorting_algorithm

    One implementation can be described as arranging the data sequence in a two-dimensional array and then sorting the columns of the array using insertion sort. The worst-case time complexity of Shellsort is an open problem and depends on the gap sequence used, with known complexities ranging from O ( n 2 ) to O ( n 4/3 ) and Θ( n log 2 n ).

  6. Comparison sort - Wikipedia

    en.wikipedia.org/wiki/Comparison_sort

    Sorting a set of unlabelled weights by weight using only a balance scale requires a comparison sort algorithm. A comparison sort is a type of sorting algorithm that only reads the list elements through a single abstract comparison operation (often a "less than or equal to" operator or a three-way comparison) that determines which of two elements should occur first in the final sorted list.

  7. Hierarchical clustering - Wikipedia

    en.wikipedia.org/wiki/Hierarchical_clustering

    The first step is to determine which elements to merge in a cluster. Usually, we want to take the two closest elements, according to the chosen distance. Optionally, one can also construct a distance matrix at this stage, where the number in the i-th row j-th column is the distance between the i-th and j-th elements. Then, as clustering ...

  8. Data orientation - Wikipedia

    en.wikipedia.org/wiki/Data_orientation

    Tabular data is two dimensional in nature - data is represented in rows and columns. However, modern operating systems logically represent data in a linear memory model, both in-disk and in-memory. [7] [8] [9] Therefore, a table in a linear memory model requires projecting its two-dimensional items in a one-dimensional space. Data orientation ...

  9. Samplesort - Wikipedia

    en.wikipedia.org/wiki/Samplesort

    Samplesort is a sorting algorithm that is a divide and conquer algorithm often used in parallel processing systems. [1] Conventional divide and conquer sorting algorithms partitions the array into sub-intervals or buckets. The buckets are then sorted individually and then concatenated together.