就像前面提到的那样，您可以简单地将两个聚合放在同一个SELECT列表中。count(*)更快。一个区别：它计数所有行，而count(fruit)只计数非空值。如果fruit是NOT NULL，两者都是一样的。

SELECT country, count(DISTINCT fruit) AS type, count(*) AS total
FROM   tbl
GROUP  BY country;

count(DISTINCT ...)比较贵。根据Postgres版本和数据分布，这可能会更快（做同样的事情）：

SELECT country, count(*) AS type, sum(fruit_ct) AS total
FROM  (
   SELECT country, fruit, count(*) AS fruit_ct
   FROM   tbl
   GROUP  BY 1, 2
   ) sub
GROUP  BY 1;

您可以将查询合并为一个：

SELECT country, COUNT(DISTINCT fruit) AS type, COUNT(fruit) as total
FROM Table
GROUP BY country;