-- Database schema
| singer : Singer_ID [ INT ] primary_key , Name [ TEXT ] , Birth_Year [ INT ] , Net_Worth_Millions [ INT ] , Citizenship [ TEXT ] | song : Song_ID [ INT ] primary_key , Title [ TEXT ] , Singer_ID [ INT ] song.Singer_ID = singer.Singer_ID , Sales [ INT ] , Highest_Position [ INT ] |
-- -- Show the names of singers that have more than one song.

SELECT T1.Name FROM singer AS T1 JOIN song AS T2 ON T1.Singer_ID  =  T2.Singer_ID GROUP BY T1.Name HAVING COUNT(*)  >  1;