[PostgreSQL] STRING_AGG
\nSELECT \n  sell_date, \n  COUNT(DISTINCT product) AS num_sold,\n  STRING_AGG(DISTINCT product, \',\') AS products\nFROM Activities\nGROUP BY sell_date\nORDER 
```\nSELECT \n  sell_date, \n  COUNT(DISTINCT product) AS num_sold,\n  STRING_AGG(DISTINCT product, \',\') AS products\nFROM Activities\nGROUP BY sell_date\nORDER BY sell_date\n\n```
['PostgreSQL']