hash_value VS sql_id

The hash value is the high speed method for locating the statement, but the unique identifier in v$sql is (hash_value, address, child_number) In Oracle 10g, there is a new column called the sql_id which is closer to unique (less chance of collision) than the hash_value, and this also has a high-speed access path into v$sql. (But again, is only unique there when combined with address and child_number)

 

Starting with Oracle Database 10g Release 1, the column SQL_ID is used to uniquely identify a cursor in views such as V$SQL and V$OPEN_CURSOR. Earlier releases use a combination of the HASH_VALUE and ADDRESS columns for this purpose.