sql - 子查询 SQL 计数函数

Question

Jurisdiction      Route
------------      -----
Portland           65
Portland           55
Cornelius          75
Cornelius          75
Cornelius          75

如何计算cornelius的路线数量？答案是 1

Answer 1

您只需要使用COUNT()和DISTINCT

select count(distinct Jurisdiction) total, Jurisdiction
from table1
where Jurisdiction = 'Cornelius'
group by Jurisdiction

请参阅带有演示的 SQL Fiddle

Answer 2

SELECT COUNT(*) 
FROM your_table 
GROUP BY Jurisdiction, Route 
WHERE Jurisdiction = 'Cornelius'

或者

SELECT COUNT(DISTINCT Route) 
FROM your_table 
GROUP BY Jurisdiction 
WHERE Jurisdiction = 'Cornelius'