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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.
The actual values are only computed when needed. For example, one could create a function that creates an infinite list (often called a stream) of Fibonacci numbers. The calculation of the n-th Fibonacci number would be merely the extraction of that element from the infinite list, forcing the evaluation of only the first n members of the list.
Introduced in Python 2.2 as an optional feature and finalized in version 2.3, generators are Python's mechanism for lazy evaluation of a function that would otherwise return a space-prohibitive or computationally intensive list. This is an example to lazily generate the prime numbers:
The relational algebra uses set union, set difference, and Cartesian product from set theory, and adds additional constraints to these operators to create new ones.. For set union and set difference, the two relations involved must be union-compatible—that is, the two relations must have the same set of attributes.
Carfentanil is 10,000 more times more potent than morphine and 100 times more potent than fentanyl, Tuell confirmed. "Even a small amount can be fatal, as it can cause respiratory failure ," he said.
Accused UnitedHealthcare CEO killer Luigi Mangione spent his first night back in the Big Apple under the same NYC federal prison as disgraced rap mogul Sean "Diddy" Combs.
Each set comes with a fitted sheet, a flat sheet and two pillow cases. Plus, these sheets have nearly 9,000 reviews on Walmart, where they have a 4.6-star rating.
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 .