SQLZOO---JOIN--11题

11、For every match involving 'POL', show the matchid, date and the number of goals scored.

答案：

SELECT matchid,mdate,count(teamid) FROM game JOIN goal ON matchid = id 

 WHERE (team1 = 'POL' OR team2 = 'POL') group by matchid,mdate

注意：GROUP BY matchid,mdate 子句中如果缺少一个条件，则该查询不通过。