UPDATE

The UPDATE operation modifies rows that already exist in a data grid table. Before calling the update() method, you must first create a row object and set the primary key columns to uniquely identify the row that is going to be updated. Next, set any non-primary key columns that must be updated. Columns that are not set are not modified in the existing row.

If a row with the primary key exists in the table, the update() method returns 1 whether or not any columns are updated. If a row with the primary key does not exist in the table, no update is done and 0 is returned.