Database: european_football_2 (difficulty: simple)
Question: What was the potiential for Joaquin on 2010/8/30?
SQL: SELECT t2.potential FROM Player AS t1 INNER JOIN Player_Attributes AS t2 ON t1.player_api_id = t2.player_api_id WHERE SUBSTR(t2.`date`, 1, 10) = '2010-08-30' AND t1.player_name = 'Joaquin'