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A cursor is a construct available in most implementations of SQL that allows the programmer to handle data in a row-by-row manner rather than as a group. Parallelizing row-by-row processing is much more complex than serial processing, which is another reason to make use of non-procedural SQL wherever possible. Database vendors typically handle parallel processing without requiring special handling by application developers. Parallel processing can be orders of magnitude faster than serial processing. == Constraints == In this article, the following constraints apply: * The term "cursor" includes all cursor-like behavior. For example, using a loop in a shell script that loops across single-row SQL queries or the output of multi-row SQL queries is cursor-like behavior and does not achieve the goal of true set-based processing within the database. * All set-based SQL must be ANSI SQL. A number of vendors provide some extremely powerful proprietary extensions. The goal is to avoid such extensions in favor of ANSI SQL. * The solution must be generalizable. In one or more examples below, specific values may be used for demonstration purposes, but any solution must scale to any number feasible within the power of the database software and machine resources. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「SQL problems requiring cursors」の詳細全文を読む スポンサード リンク
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