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The joined table retains each row—even if no other matching row exists. Outer joins subdivide further into left outer joins, right outer joins, and full outer joins, depending on which table's rows are retained: left, right, or both (in this case left and right refer to the two sides of the JOIN keyword).
The outer join ( ) or full outer join in effect combines the results of the left and right outer joins. The full outer join is written as R S where R and S are relations. [f] The result of the full outer join is the set of all combinations of tuples in R and S that are equal on their common attribute names, in addition to tuples in S that have ...
A block-nested loop (BNL) is an algorithm used to join two relations in a relational database. [1]This algorithm [2] is a variation of the simple nested loop join and joins two relations and (the "outer" and "inner" join operands, respectively).
A right join is employed over the Target (the INTO table) and the Source (the USING table / view / sub-query)--where Target is the left table and Source is the right one. The four possible combinations yield these rules:
In SQL the UNION clause combines the results of two SQL queries into a single table of all matching rows.The two queries must result in the same number of columns and compatible data types in order to unite.
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The sort-merge join (also known as merge join) is a join algorithm and is used in the implementation of a relational database management system. The basic problem of a join algorithm is to find, for each distinct value of the join attribute, the set of tuples in each relation which display that value. The key idea of the sort-merge algorithm is ...
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