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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. PHP syntax and semantics - Wikipedia

    en.wikipedia.org/wiki/PHP_syntax_and_semantics

    PHP treats newlines as whitespace, in the manner of a free-form language. The concatenation operator is . (dot). Array elements are accessed and set with square brackets in both associative arrays and indexed arrays. Curly brackets can be used to access array elements, but not to assign.

  4. Open addressing - Wikipedia

    en.wikipedia.org/wiki/Open_addressing

    Hash collision resolved by linear probing (interval=1). Open addressing, or closed hashing, is a method of collision resolution in hash tables.With this method a hash collision is resolved by probing, or searching through alternative locations in the array (the probe sequence) until either the target record is found, or an unused array slot is found, which indicates that there is no such key ...

  5. Database storage structures - Wikipedia

    en.wikipedia.org/wiki/Database_storage_structures

    Index is a full index so data file does not have to be ordered; Pros and cons versatile data structure – sequential as well as random access; access is fast; supports exact, range, part key and pattern matches efficiently. volatile files are handled efficiently because index is dynamic – expands and contracts as table grows and shrinks

  6. Trino (SQL query engine) - Wikipedia

    en.wikipedia.org/wiki/Trino_(SQL_query_engine)

    Trino is an open-source distributed SQL query engine designed to query large data sets distributed over one or more heterogeneous data sources. [1] Trino can query data lakes that contain open column-oriented data file formats like ORC or Parquet [2] [3] residing on different storage systems like HDFS, AWS S3, Google Cloud Storage, or Azure Blob Storage [4] using the Hive [2] and Iceberg [3 ...

  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. Key–value database - Wikipedia

    en.wikipedia.org/wiki/Key–value_database

    A tabular data card proposed for Babbage's Analytical Engine showing a key–value pair, in this instance a number and its base-ten logarithm. A key–value database, or key–value 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.

  9. 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.