| 摘要 |
PROBLEM TO BE SOLVED: To provide a database system which can join tables at high speed with a minimum required memory capacity in a relational database system. SOLUTION: A largest number of column table extracting means 66 extracts one table including a column to be retrieved from a plurality of tables. An identical data selection column excluding means 67 performs processing to exclude the columns of the other tables. which are not extracted yet and store the same data contents as data content of the column of the table extracted by the largest number of column table extracting means 66, from joining processing objects in subsequent table joining processing. A table joining means 68 repetitively performs processing by the largest number of column table extracting means 66 and processing by the identical data selection column excluding means 67 till the whole columns to be retrieved are analyzed, and then, joins the tables which are successively extracted by the largest number of column table extracting means 66. COPYRIGHT: (C)2009,JPO&INPIT
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