System and method for maintaining a user's state within a database table and for accommodating null values

A method for maintaining a user's state within a database table, the method comprising the steps of:

• receiving a request for a first batch of records from a database server;
• retrieving the first batch of records from the database server;
• determining a minimum value and a maximum value for a first field in the first batch of records;
• determining a minimum value and a maximum value for a second field in the first batch of records;
• receiving a request for a second batch of records;
• in response to a determination that the request for the second batch of records is a next request and that the first field is arranged in ascending order and the second field is arranged in descending order, retrieving the second batch of records from the database server, wherein the second batch of records contains a first value in the first field that is greater than the maximum value for the first field in the first batch of records, or wherein the second batch of records contains a second value in the second field that is less than the minimum value for the second field in the first batch of records;
• in response to a determination that the request for the second batch of records is a next request and that the first field is arranged in descending order and the second field is arranged in ascending order, retrieving the second batch of records from the database server, wherein the second batch of records contains a first value in the first field that is less than the minimum value for the first field in the first batch of records, or wherein the second batch of records contains a second value in the second field that is greater than the maximum value for the second field in the first batch of records;
• in response to a determination that the request for the second batch of records is a previous request and that the first field is arranged in ascending order and the second field is arranged in descending order, retrieving the second batch of records from the database server, wherein the second batch of records contains a first value in the first field that is less than the minimum value for the first field in the first batch of records, or wherein the second batch of records contains a second value in the second field that is greater than the maximum value for the second field in the first batch of records;
• and
• in response to a determination that the request for the second batch of records is a previous request and that the first field is arranged in descending order and the second field is arranged in ascending order, retrieving the second batch of records from the database server, wherein the second batch of records contains a first value in the first field that is greater than the maximum value for the first field in the first batch of records, or wherein the second batch of records contains a second value in the second field that is less than the minimum value for the second field in the first batch of records.

A system for maintaining a user's state within a database table comprising:

• a database server operative for maintaining a plurality of database records;
• a client computer, operative for presenting a batch of database records to the user;
• a web server operative for retrieving a batch of database records from the database server and for providing the batch of database records to the client computer and for accounting for null values within the batch of database records retrieved;
• wherein the client computer is further operative for storing at least one field value contained in a retrieved batch of database records;
• and
• wherein the web server is further operative to determine which batch of records to be retrieved from the database server, based on the field value stored by the client computer and on whether the retrieved batch of database records comprises a null value.

A computer-readable medium having computer-executable instructions for performing steps comprising:

• receiving a request for a first batch of records from a database table on a database server;
• retrieving the first batch of record from the database server;
• determining a minimum value and a maximum value for at least one field in the first batch of records;
• receiving a request for a second batch of records;
• and
• making a determination as to which records in the database server to retrieve, based on the maximum value or the minimum value and on whether the second batch of records comprises a null value.

The computer-readable medium of 28, wherein the step of making a determination as to which records in the database server to retrieve comprises:

• in response to a determination that the request for the second batch of records is a next request and that the second batch of records are arranged in ascending order, retrieving the second batch of records from the database server such that the second batch contains a value for the at least one field that is greater than the maximum value of the at least one field in the first batch of records;
• in response to a determination that the request for the second batch of records is a next request and that the second batch of records are arranged in descending order, retrieving the second batch of records from the database server such that the second batch contains a value for the at least one field that is less than the minimum value of the at least one field in the first batch of records;
• in response to a determination that the request for the second batch of records is a previous request and that the second batch of records are arranged in ascending order, retrieving the second batch of records from the database server such that the second batch contains a value for the at least one field that is less than the minimum value of the at least one field in the first batch of records;
• and
• in response to a determination that the request for the second batch of records is a previous request and that the second batch of records are arranged in descending order, retrieving the second batch of records from the database server such that the second batch contains a value for the at least one field that is greater than the minimum value of the at least one field in the first batch of records.

A computer-readable medium having computer-executable instructions for performing steps comprising:

• receiving a request for a first batch of records from a database table on a database server;
• retrieving the first batch of record from the database server;
• determining a minimum value and maximum value for at least one field in the first batch of records;
• receiving a request for a second batch of records;
• in response to a determination that the request for the second batch of records is a next request and that the second batch of records are arranged in ascending order, retrieving the second batch of records from the database server such that the second batch contains a value for the at least one field that is greater than the maximum value of the at least one field in the first batch of records;
• in response to a determination that the request for the second batch of records is a next request and that the second batch of records are arranged in descending order, retrieving the second batch of records from the database server such that the second batch contains a value for the at least one field that is less than the minimum value of the at least one field in the first batch of records;
• in response to a determination that the request for the second batch of records is a previous request and that the second batch of records are arranged in ascending order, retrieving the second batch of records from the database server such that the second batch contains a value for the at least one field that is less than the minimum value of the at least one field in the first batch of records;
• and
• in response to a determination that the request for the second batch of records is a previous request and that the second batch of records are arranged in descending order, retrieving the second batch of records from the database server such that the second batch contains a value for the at least one field that is greater than the minimum value of the at least one field in the first batch of records.