Append rows to a target table: Using the ALTER TABLE APPEND command,you can now append rows to a target table. When you issue this command, Amazon Redshift moves the data from the source table to matching columns in the target table. ALTER TABLE APPEND is normally much faster than a similar CREATE TABLE AS or INSERT INTO operation because it moves the data instead of duplicating it. This could be particularly useful in cases where you load data into a staging table, and process it,and then copy the results into a production table. For more details, refer to the ALTER TABLE APPEND command.
Source: amazon.com