MySQL通过查询包括组中的0个计数项

Question

我有类似的查询：

SELECT Zip, COUNT(*) as count 
FROM people 
WHERE specialty='Driver' 
GROUP BY Zip 
ORDER BY Zip

它使用0计数过滤掉结果，但即使计数为0，我仍然需要所有分组的拉链。

Answer 1

您可以使用条件聚合

SELECT Zip, SUM(specialty = 'Driver') as count 
FROM people 
GROUP BY Zip 
ORDER BY Zip