Question

我有一张桌子：Country Varchar（20），City Varchar（20），Street Varchar（20）

我想计算所有城市的街道，如果其中一个是主街

它应该是这样的......

SELECT Country, City, Count(Street)
FROM Streets
GROUP BY Country, City;

我不知道如何检查其中一个街道名称是否是Main Street我该怎么办？

Answer 1

您可以使用having：

SELECT Country, City, Count(Street)
FROM Streets
GROUP BY Country, City
HAVING SUM(CASE WHEN Street = 'Main Street' THEN 1 ELSE 0 END) > 0;

Answer 2

你可以简单地使用它。

SELECT Country, City, Count(Street) FROM Streets where upper(streets)='MAIN STREET' GROUP BY Country, City;

Answer 3

您可以在WHERE子句中使用子查询来查找所有拥有主街的城市：

SELECT COUNTRY, CITY, COUNT(STREETS)
  FROM STREETS
  WHERE (COUNTRY, CITY) IN (SELECT DISTINCT COUNTRY, CITY
                              FROM STREETS
                              WHERE UPPER(STREET) = 'MAIN STREET')
  GROUP BY COUNTRY, CITY

或者您可以使用联接

SELECT s.COUNTRY, s.CITY, COUNT(s.STREETS)
  FROM STREETS s
  INNER JOIN (SELECT DISTINCT COUNTRY, CITY
                FROM STREETS
                WHERE LOWER(STREET) = 'main street') c
    ON c.COUNTRY = s.COUNTRY AND
       c.CITY = s.CITY

或者您可以使用公用表表达式：

WITH cteCITIES_WITH_MAIN_STREET AS (SELECT DISTINCT COUNTRY, CITY
                                      FROM STREETS
                                      WHERE INITCAP(STREET) = 'Main Street')
SELECT s.COUNTRY, s.CITY, COUNT(s.STREETS)
  FROM STREETS s
  INNER JOIN cteCITIES_WITH_MAIN_STREET c
    ON c.COUNTRY = s.COUNTRY AND
       c.CITY = s.CITY

注意：未在动物身上进行过测试;你会先成为第一个！： - ）

祝你好运。

如果其中一个满足条件，则选择COUNT

3 个答案: