带有计数的SQL LEFT OUTER JOIN

Question

我在这里有此查询：

SELECT a.timeSlot, a.dateSlot, COUNT(concat(b.dateSlot, ' - ', b.timeSlot)) AS counter 
FROM CP_VIP_Preview_TimeSlots as a 
   LEFT OUTER JOIN [CP-VIP-Preview] as b 
                ON a.timeSlot = b.dateSlot 
               AND a.dateSlot = b.timeSlot 
GROUP BY a.timeSlot, a.dateSlot, a.[order] 
ORDER BY a.[order]

我想做的是获取每个查询的计数，但是查询有些混乱，任何具有0的行都显示为1，而实际上具有项目的任何行都显示正确的数字，如果该行存在问题count是0，它显示1.。为什么这样做？

Answer 1

您的COUNT(concat(b.dateSlot, ' - ', b.timeSlot))将始终返回至少一个

也许你可以尝试

sum(IIF(b.dateSlot is null,0,1))

Answer 2

您需要使用HAVING在使用分组依据之后应用过滤器，这样就不会将记录计数为零

SELECT a.timeSlot, a.dateSlot, COUNT(concat(b.dateSlot, ' - ', b.timeSlot)) AS counter 
FROM CP_VIP_Preview_TimeSlots as a 
   LEFT OUTER JOIN [CP-VIP-Preview] as b 
                ON a.timeSlot = b.dateSlot 
               AND a.dateSlot = b.timeSlot 
GROUP BY a.timeSlot, a.dateSlot, a.[order] 
ORDER BY a.[order]

HAVING COUNT（concat（b.dateSlot，'-'，b.timeSlot））> 0