how to index the following data (code ascending and amount descending)

before:
code amount
---- ------
AAA 100.00
AAA 50.00
BBB 200.00
CCC 250.00
AAA 300.00
CCC 500.00
BBB 100.00

after:
code amount
---- ------
AAA 300.00
AAA 100.00
AAA 50.00
BBB 200.00
BBB 100.00
CCC 500.00
CCC 250.00

TQ.