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In a SQL database query, a correlated subquery (also known as a synchronized subquery) is a subquery (a query nested inside another query) that uses values from the outer query. This can have major impact on performance because the correlated subquery might get recomputed every time for each row of the outer query is processed.
In relational databases, a nested table is a table that is embedded within another table. Individual elements can be inserted, updated, and deleted in a nested table. Since individual elements can be modified in a nested table, they are more flexible than an array because elements in an array can only be modified as a whole, not individually. A ...
SQL statements also include the semicolon (";") statement terminator. Though not required on every platform, it is defined as a standard part of the SQL grammar. Insignificant whitespace is generally ignored in SQL statements and queries, making it easier to format SQL code for readability.
Articles with example SQL code (28 P) C. SQL ... SQL data access (14 P) SQL keywords (20 P) SQLite (1 C, 4 P) Pages in category "SQL" ... (SQL statements) Check ...
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".
Actual SQL implementations normally use other approaches, such as hash joins or sort-merge joins, since computing the Cartesian product is slower and would often require a prohibitively large amount of memory to store. SQL specifies two different syntactical ways to express joins: the "explicit join notation" and the "implicit join notation".
Buckwheat. Despite its name, buckwheat doesn’t contain any wheat at all, making it a popular grain in gluten-free diets. While buckwheat groats, or kernels, contain a good amount of protein ...
Nested transactions, for example, are transactions which contain statements within them that start new transactions (i.e. sub-transactions). Multi-level transactions are a variant of nested transactions where the sub-transactions take place at different levels of a layered system architecture (e.g., with one operation at the database-engine ...