| 翻訳と辞書 |
| Full table scan ： ウィキペディア英語版 |
Full table scan
Full table scan (also known as sequential scan) is a scan made on a database where each row of the table under scan is read in a sequential (serial) order and the columns encountered are checked for the validity of a condition.〔(【引用サイトリンク】title=Avoiding Table Scans )〕 Full table scans are usually〔(【引用サイトリンク】title=Which is Faster: Index Access or Table Scan? )〕 the slowest method of scanning a table due to the heavy amount of I/O reads required from the disk which consists of multiple seeks as well as costly disk to memory transfers. Sequential scan takes place usually when the column or group of columns of a table (the table may be on disk or may be an intermediate table created by the join of two or more tables) needed for the scan do not contain an index which can be used for the purpose.
== References ==
〔
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「Full table scan」の詳細全文を読む
スポンサード リンク
| 翻訳と辞書 : 翻訳のためのインターネットリソース |
Copyright(C) kotoba.ne.jp 1997-2016. All Rights Reserved.
|
|