Abstract: A database query compiler and compilation method has special facilities for compiling a query that includes an Offset sequence function, Offset(argument, index). During execution of the query, while the cursor for a table is pointing to a current row, the Offset function is used to access information from a previously accessed row. The argument of the Offset sequence function is a specified function of information associated with the previously accessed row of the table. The previously accessed row has a position that is index rows before the current row referenced by the cursor for the table. During compilation, the argument of the Offset sequence function is parsed to determine a set of auxiliary fields for each row of the table. Each auxiliary field of a row contains information that may be accessed during execution of the Offset sequence function while the cursor for that table is pointing to a subsequent row.

Abstract: A database query compiler and compilation method has special facilities for compiling a query that includes a Rows Since sequence function, Rows Since (search condition). A query normalizer includes a Rows Since function normalizer for normalizing the Rows Since sequence function. The Rows Since function normalizer parses the search condition of the Rows Since function to identify each reference to information from a previously access row and converts each such identified reference into an Offset sequence function, Offset(argument, index). The argument of the Offset sequence function is a specified function of the identified information from a previously accessed row of the table. The previously accessed row has a position that is index rows before the current row referenced by the cursor for the table. The query compiler places the resulting normalized search condition in a search loop that traverses successively earlier rows in the table until it finds a row that satisfies the search condition.