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  2. Unique identifier - Wikipedia

    en.wikipedia.org/wiki/Unique_identifier

    A unique identifier (UID) is an identifier that is guaranteed to be unique among all identifiers used for those objects and for a specific purpose. [1] The concept was formalized early in the development of computer science and information systems .

  3. Surrogate key - Wikipedia

    en.wikipedia.org/wiki/Surrogate_key

    The unique index serves two purposes: (i) to enforce entity integrity, since primary key data must be unique across rows and (ii) to quickly search for rows when queried. Since surrogate keys replace a table's identifying attributes—the natural key —and since the identifying attributes are likely to be those queried, then the query ...

  4. Unique molecular identifier - Wikipedia

    en.wikipedia.org/wiki/Unique_molecular_identifier

    Unique molecular identifiers (UMIs), or molecular barcodes (MBC) are short sequences or molecular "tags" added to DNA fragments in some next generation sequencing ...

  5. Universally unique identifier - Wikipedia

    en.wikipedia.org/wiki/Universally_unique_identifier

    A Universally Unique Identifier (UUID) is a 128-bit label used to uniquely identify objects in computer systems. The term Globally Unique Identifier (GUID) is also used, mostly in Microsoft systems. [1] [2] When generated according to the standard methods, UUIDs are, for practical purposes, unique.

  6. Database index - Wikipedia

    en.wikipedia.org/wiki/Database_index

    A database index is a data structure that improves the speed of data retrieval operations on a database table at the cost of additional writes and storage space to maintain the index data structure. Indexes are used to quickly locate data without having to search every row in a database table every time said table is accessed.

  7. Index of a subgroup - Wikipedia

    en.wikipedia.org/wiki/Index_of_a_subgroup

    A subgroup H of finite index in a group G (finite or infinite) always contains a normal subgroup N (of G), also of finite index. In fact, if H has index n, then the index of N will be some divisor of n! and a multiple of n; indeed, N can be taken to be the kernel of the natural homomorphism from G to the permutation group of the left (or right ...

  8. Why I Can't Stop Buying This Ultra-High-Yielding ETF - AOL

    www.aol.com/why-cant-stop-buying-ultra-095100574...

    JPMorgan Nasdaq Premium Income ETF is a rather unique ETF. It aims to deliver monthly distributable income and exposure to the high-growth Nasdaq-100 Index with less volatility. The income comes ...

  9. Uniform Resource Name - Wikipedia

    en.wikipedia.org/wiki/Uniform_resource_name

    A Uniform Resource Name (URN) is a Uniform Resource Identifier (URI) that uses the urn scheme.URNs are globally unique persistent identifiers assigned within defined namespaces so they will be available for a long period of time, even after the resource which they identify ceases to exist or becomes unavailable. [1]