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SQL Anywhere 11.0.0 » SQL Anywhere Server - SQL Usage » Query Optimizer » Query optimization and execution » Query execution algorithms » Join algorithms

 

NestedLoopsAntisemijoin algorithm (JNLA)

Similar to the NestedLoopsJoin algorithm, NestedLoopsAntisemijoin joins its inputs by scanning the right-hand side for each row of the left-hand side. As with NestedLoopsJoin, the right-hand side may be read many times, so for larger inputs an index scan is preferable. NestedLoopsAntisemijoin differs from NestedLoopsJoin in that it only outputs values from the left-hand side; the right-hand side is used only for restricting which rows of the left-hand side appear in the result. Specifically, values from the left-hand side are only included if they have no corresponding value on the right-hand side.