我有2张桌子，而且我应该每天保留红船的数量
我让它只返回非0的值，我无法弄清楚如何包含0
我的查询
select r.day, count(distinct r.bname)
from reservation r, boat b
where r.bname = b.bname and color = 'red'
group by day
此查询打印出所有返回非零值的行
如何包含零值？
我尝试过使用左连接但没有运气......或者可能是我做错了
Table Attributes
sailor| sname rating
Brutus 1
Andy 8
Horatio 7
Rusty 8
Bob 1
boat|bname color rating
SpeedQueen white 9
Interlake red 8
Marine blue 7
Bay red 3
reservation| sname bname day
Andy Interlake Monday
Andy Bay Wednesday
Andy Marine Saturday
Rusty Bay Sunday
Rusty Interlake Wednesday
Rusty Marine Wednesday
Bob Bay Monday
alldays| day
monday
tuesday
wednesday
thursday
friday
saturday
sunday
我的查询打印出来
Monday 2
Wednesday 2
Sunday 1
当我需要它像这样做
Monday 2
Tuesday 0
Wednesday 2
Thursday 0
Friday 0
Saturday 0
Sunday 1
我理解，因为sqlite3不返回空值，我需要进行连接才能获得这些值？但我试过它不工作