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  2. Nested set model - Wikipedia

    en.wikipedia.org/wiki/Nested_set_model

    The nested set model is a technique for representing nested set collections (also known as trees or hierarchies) in relational databases.. It is based on Nested Intervals, that "are immune to hierarchy reorganization problem, and allow answering ancestor path hierarchical queries algorithmically — without accessing the stored hierarchy relation".

  3. Key–value database - Wikipedia

    en.wikipedia.org/wiki/Keyvalue_database

    A tabular data card proposed for Babbage's Analytical Engine showing a keyvalue pair, in this instance a number and its base-ten logarithm. A keyvalue database, or keyvalue store, is a data storage paradigm designed for storing, retrieving, and managing associative arrays, and a data structure more commonly known today as a dictionary or hash table.

  4. Ordered Key-Value Store - Wikipedia

    en.wikipedia.org/wiki/Ordered_Key-Value_Store

    An Ordered Key-Value Store (OKVS) is a type of data storage paradigm that can support multi-model database. An OKVS is an ordered mapping of bytes to bytes. An OKVS will keep the key-value pairs sorted by the key lexicographic order. OKVS systems provides different set of features and performance trade-offs.

  5. Entity–attribute–value model - Wikipedia

    en.wikipedia.org/wiki/Entity–attribute–value...

    In each table, the "entity" is a composite of the patient ID and the date/time the diagnosis was made (or the surgery or lab test performed); the attribute is a foreign key into a specially designated lookup table that contains a controlled vocabulary - e.g., ICD-10 for diagnoses, Current Procedural Terminology for surgical procedures, with a ...

  6. Database model - Wikipedia

    en.wikipedia.org/wiki/Database_model

    A key that can be used to uniquely identify a row in a table is called a primary key. Keys are commonly used to join or combine data from two or more tables. For example, an Employee table may contain a column named Location which contains a value that matches the key of a Location table.

  7. Database index - Wikipedia

    en.wikipedia.org/wiki/Database_index

    The records for the tables sharing the value of a cluster key shall be stored together in the same or nearby data blocks. This may improve the joins of these tables on the cluster key, since the matching records are stored together and less I/O is required to locate them. [2]

  8. Associative array - Wikipedia

    en.wikipedia.org/wiki/Associative_array

    The basic idea behind a hash table is that accessing an element of an array via its index is a simple, constant-time operation. Therefore, the average overhead of an operation for a hash table is only the computation of the key's hash, combined with accessing the corresponding bucket within the array. As such, hash tables usually perform in O(1 ...

  9. Lightning Memory-Mapped Database - Wikipedia

    en.wikipedia.org/wiki/Lightning_Memory-Mapped...

    Lightning Memory-Mapped Database (LMDB) is an embedded transactional database in the form of a key-value store. LMDB is written in C with API bindings for several programming languages . LMDB stores arbitrary key/data pairs as byte arrays, has a range-based search capability, supports multiple data items for a single key and has a special mode ...