Record retrieval method using key bondary value table and condition valid status table

A record retrieval method in a data processing apparatus which has a data file for storing a plurality of records each identified by a keyword and which performs a records operation in response to an OR designation of record retrieval conditions constituted by a combination of the keywords so as to read out records satisfying the conditions from the data file, comprising the computer implemented steps of:

• extracting keywords representing a boundary of the record retrieval condition;
• preparing a keyword boundary table in which the extracted keywords are arranged in the order in which they were extracted in the extracting step, and then sorting the extracted keywords;
• storing in a condition valid status table a start flag and an end flag representing a valid range of the record retrieval condition, the condition valid status table comprising m rows.times.n columns (where m and n are integers of 1 or more), rows of said condition valid status table corresponding to the keywords in the keyword boundary table and columns of said condition valid status table corresponding to the record retrieval conditions, respectively;
• sorting the contents of the condition valid status table in accordance with the contents of the keyword boundary table;
• searching the condition valid status table in units of columns and rows for updating flags in the condition valid status table, and storing an updated flag in an area at the intersection of the mth row and the nth column in the condition valid status table, the updated flag representing whether a condition corresponding to the nth column in the condition valid status table is valid for record retrieval in the boundary range of the mth row to the (m+1)th row in the keyword boundary table;
• and
• reading out records in the order of the keywords from the data file, determining that a read out record belongs to the mth row in the keyword boundary table, and determining that the read out record is one satisfying the designated record retrieval condition if the valid flag exists in the area at the intersection of the mth row and the column corresponding to the designated record retrieval condition in the condition valid status table.