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The Nested Set model is appropriate where the tree element and one or two attributes are the only data, but is a poor choice when more complex relational data exists for the elements in the tree. Given an arbitrary starting depth for a category of 'Vehicles' and a child of 'Cars' with a child of 'Mercedes', a foreign key table relationship must ...
Using a database-specific stored procedure that generates the surrogate key, performs the INSERT operation, and finally returns the generated key. For example, in Microsoft SQL Server, the key is retrieved via the SCOPE_IDENTITY() special function, while in SQLite the function is named last_insert_rowid().
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. Keys are also critical in the creation of indexes, which ...
For table markup, it can be applied to whole tables, table captions, table rows, and individual cells. CSS specificity in relation to content should be considered since applying it to a row could affect all that row's cells and applying it to a table could affect all the table's cells and caption, where styles closer to the content can override ...
Set operations in SQL is a type of operations which allow the results of multiple queries to be combined into a single result set. [ 1 ] Set operators in SQL include UNION , INTERSECT , and EXCEPT , which mathematically correspond to the concepts of union , intersection and set difference .
Both 2NF and 3NF are concerned equally with all candidate keys of a table and not just any one key. Chris Date refers to Kent's summary as "an intuitively attractive characterization" of 3NF and notes that with slight adaptation it may serve as a definition of the slightly stronger Boyce–Codd normal form: "Each attribute must represent a fact ...
In Miranda, this right-fold, from Hughes (1989:5-6), has the same semantics (by example) as the Scheme implementation above, for two arguments. append a b = reduce cons b a Where reduce is Miranda's name for fold, and cons constructs a list from two values or lists. For example,
MySQL, MariaDB: own stored procedures, closely adhering to SQL/PSM standard NuoDB: SQL or Java: OpenLink Virtuoso: Virtuoso SQL Procedures (VSP); [2] also extensible via Java, C, and other programming languages Oracle: PL/SQL or Java: PostgreSQL: PL/pgSQL, can also use own function languages such as PL/Tcl, PL/Perl or PL/Python [3] SAP HANA ...