This command copies the value stored at the source key to the destination
key.
By default, the destination key is created in the logical database used by the
connection. The DB option allows specifying an alternative logical database
index for the destination key. The REPLACE option removes the destination
key before copying the value to it.
The command returns zero when the source key does not exist or when the
destination key already exists and the REPLACE option is not specified.
Examples
SET dolly "sheep"
COPY dolly clone
GET clone