Generating Nested SQL Queries for Documentation

概要

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In this paper, we develop procedures to transform a user's query into a nested form suitable for query documentation, editing, and reusability purposes. We discuss generating nested form of the three query types : chain, tree, and cyclic. For tree and cyclic queries, there may be more than one nested form. Thus, we have to determine the order of writing query blocks. we use the notion of join strength. Joins are classified by their strength of relationship. Strong joins are selected to connect adjacent query blocks. For a tree query, the first blocks is selected by the output attribute, the second one is selected as that of strongest join with the previous block and so on. Chain queries are handled as a special case of tree queries. A cyclic query cannot be written in the nested form. A form which is in part nested and in part unnested, called seminested form is used. This form is generated by first finding a minimum spanning tree of the cyclic query graph. This tree contains most strong joins. We discuss aiso the case when the query output is obtained from multiple blocks. Since it is not possible to write such a query in the nested form, the query is convertedi nto a modified nested query in which the output is obtained from only one block.
一般社団法人情報処理学会の論文
1994-02-15