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DELETE requires a shared table lock; Triggers fire; DELETE can be used in the case of: database link; DELETE returns the number of records deleted; Transaction log - DELETE needs to read records, check constraints, update block, update indexes, and generate redo / undo. All of this takes time, hence it takes time much longer than with TRUNCATE
A hierarchical query is a type of SQL query that handles hierarchical model data. They are special cases of more general recursive fixpoint queries, which compute transitive closures . In standard SQL:1999 hierarchical queries are implemented by way of recursive common table expressions (CTEs).
ArangoDB is a transactional native multi-model database supporting two major NoSQL data models (graph and document [1]) with one query language. Written in C++ and optimized for in-memory computing. In addition ArangoDB integrated RocksDB for persistent storage. ArangoDB supports Java, JavaScript, Python, PHP, NodeJS, C++ and Elixir.
Nested Sets is a clever solution – maybe too clever. It also fails to support referential integrity. It’s best used when you need to query a tree more frequently than you need to modify the tree. [9] The model doesn't allow for multiple parent categories. For example, an 'Oak' could be a child of 'Tree-Type', but also 'Wood-Type'.
Application node or SQL node (mysqld process): A MySQL server (mysqld) that connects to all of the data nodes in order to perform data storage and retrieval. This node type is optional; it is possible to query data nodes directly via the NDB API, either natively using the C++ API or one of the additional NoSQL APIs described above.
For example, in a phone book organized by city first, then by last name, and then by first name, in a particular city, one can easily extract the list of all phone numbers. However, it would be very tedious to find all the phone numbers for a particular last name. One would have to look within each city's section for the entries with that last ...
SingleStore can store data in either row-oriented tables ("rowstores") or column-oriented tables ("columnstores"). The format used is determined by the user when creating the table. [29] Rowstore tables, as the name implies, store information in row format, which is the traditional data format used by RDBMS systems.
Relations among tables are mapped in the same way: by convention. For instance, to create a one-to-many relationship between two tables one assigns an array to the property bearing the name of the target table. This automatically creates the table as well as the required columns. Code example, demonstrating a simple CRUD operation and a relation: