Method of data structure extraction for computer systems operating under the ANSI-92 SQL2 outer join protocol

Claim 1

A computer system using the ANSI-92 SQL2 outer join protocol for manipulating data contained in the computer system to create and store a resultant database having a known hierarchial data structure represented by an outer join protocol statement, the computer system comprising: a) a central processing unit coupled with a first memory storage means containing at least a first normalized, relational database, each database in said first storage means including a plurality of data having a known hierarchial data structure capable of being represented in a protocol equivalent to ANSI-92 SQL2 outer join grammar, said central processing unit operating in accord with a programmed set of instructions having a protocol equivalent to ANSI-92 SQL2 outer join grammar; b) second memory means coupled to said central processing unit having a push-pop stack area and a storage area for nodes; c) said first memory means further containing a set of instructions for controlling said central processing unit to execute the following steps: (i) parsing the outer join protocol statement into a plurality of tokens for execution by said central processing unit in accord with the grammar, syntax and semantics, of ANSI-92 SQL2 outer join protocol for controlling the actions of said central processing unit; (ii) parsing sequentially said tokens from the outer join statement to identify if the token being parsed is a table name, join type (left or right), or a join condition; (iii) pushing a new root structural node datum with table name onto said push-pop stack in said second memory means as a data item if the token being parsed is identified as a table name; (iv) pushing a join type datum representative of a left or right join type token onto said push-pop stack in said second memory means as a data item, if the token being parsed is identified as a left or right join type token respectively; (v) repeating steps (ii) to (iv) until the token being parsed is identified as a join condition token; (vi) popping the top three data items from said push-pop stack in said second memory means representing a right database root structural node token, a join type token (left or right), and a left database structural root node token; (vii) linking the right and left node structures represented by the popped root node data into one structure at the structural node points specified by the current join condition token where the lowest level table referenced from said join condition in left and right structures are the link node points and the popped join type (right or left) specifies which substructure assumes the higher level position of the combined structure; (viii) pushing a root node datum representative of the resulting node structure back onto said push-pop stack in the second memory means; (ix) repeating steps (ii) through (viii) until all tokens from the outer join statement have been processed; and, (x) ordering the node data represented by the resulting root node on said push-pop stack in the second memory means in accordance with the hierarchial data structure and storing the ordered node data in said first memory means.