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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.
SELECT is the most common operation in SQL, called "the query". SELECT retrieves data from one or more tables, or expressions. Standard SELECT statements have no persistent effects on the database. Some non-standard implementations of SELECT can have persistent effects, such as the SELECT INTO syntax provided in some databases. [4]
An equi-join is a specific type of comparator-based join, that uses only equality comparisons in the join-predicate. Using other comparison operators (such as <) disqualifies a join as an equi-join. The query shown above has already provided an example of an equi-join:
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WASHINGTON (Reuters) -U.S. officials are communicating with people in Syria to seek information about Austin Tice, an American journalist captured there more than 12 years ago, White House ...
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.
Oceana, a conservation group based in D.C., has reported numerous collisions between North Atlantic right whales and boats. These collisions have resulted in the deaths of right whales.
Machine Gun Kelly is "doing the best he can" to get back together with Megan Fox following their breakup, with sources claiming the rapper "remains hopeful."