用于COUNT命令在MYSQL中创建查询

Question

下面显示了我原来的MY SQL表格。

SELECT name, COUNT(city) AS "count_no"
FROM emp
GROUP BY name
ORDER BY count_no DESC;

我需要以下结果。

SAM有4条记录。但伦敦有两个城市的记录。 我需要 SAM记录中有多少个不同的城市。 我做了很多查询，但是无法创建我的SQL查询。

Answer 1

将DISTINCT添加到count参数：

SELECT name, COUNT(DISTINCT city) AS "count_no"
FROM emp
GROUP BY name
ORDER BY count_no DESC;

Answer 2

SELECT name, COUNT(DISTINCT city) AS "count_no"
FROM emp
GROUP BY name
ORDER BY count_no DESC;