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  2. Candidate key - Wikipedia

    en.wikipedia.org/wiki/Candidate_key

    A candidate key, or simply a key, of a relational database is any set of columns that have a unique combination of values in each row, with the additional constraint that removing any column could produce duplicate combinations of values. A candidate key is a minimal superkey, [1] i.e., a superkey that does not contain a smaller one. Therefore ...

  3. Database normalization - Wikipedia

    en.wikipedia.org/wiki/Database_normalization

    In situations where the number of unique values of a column is far less than the number of rows in the table, column-oriented storage allow significant savings in space through data compression. Columnar storage also allows fast execution of range queries (e.g., show all records where a particular column is between X and Y, or less than X.)

  4. Data deduplication - Wikipedia

    en.wikipedia.org/wiki/Data_deduplication

    In computing, data deduplication is a technique for eliminating duplicate copies of repeating data. Successful implementation of the technique can improve storage utilization, which may in turn lower capital expenditure by reducing the overall amount of storage media required to meet storage capacity needs.

  5. Join (SQL) - Wikipedia

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

    A join clause in the Structured Query Language combines columns from one or more tables into a new table. The operation corresponds to a join operation in relational algebra. Informally, a join stitches two tables and puts on the same row records with matching fields : INNER, LEFT OUTER, RIGHT OUTER, FULL OUTER and CROSS.

  6. dplyr - Wikipedia

    en.wikipedia.org/wiki/Dplyr

    dplyr is an R package whose set of functions are designed to enable dataframe (a spreadsheet-like data structure) manipulation in an intuitive, user-friendly way. It is one of the core packages of the popular tidyverse set of packages in the R programming language. [1]

  7. Bloom filter - Wikipedia

    en.wikipedia.org/wiki/Bloom_filter

    The delete operation then consists of decrementing the value of each of the respective buckets. Arithmetic overflow of the buckets is a problem and the buckets should be sufficiently large to make this case rare. If it does occur then the increment and decrement operations must leave the bucket set to the maximum possible value in order to ...

  8. Stack Overflow - Wikipedia

    en.wikipedia.org/wiki/Stack_Overflow

    Top Stack Overflow tags. A 2013 study has found that 75% of users only ask one question, 65% only answer one question, and only 8% of users answer more than 5 questions. [34] To empower a wider group of users to ask questions and then answer, Stack Overflow created a mentorship program resulting in users having a 50% increase in score on ...

  9. Object copying - Wikipedia

    en.wikipedia.org/wiki/Object_copying

    To effect the creation of a new object which is a shallow duplicate of y, the feature twin is used. In this case, one new object is created with its fields identical to those of the source. The feature twin relies on the feature copy, which can be redefined in descendants of ANY, if needed. The result of twin is of the anchored type like Current.