Question

我正在尝试列出所有Land.name，它们具有的平均冰山数量和冰山数量均大于平均数量。

CREATE TABLE Land( 
  c_namn VARCHAR(50) NOT NULL UNIQUE,
  code VARCHAR(4) 
);

CREATE TABLE Berg(
  land VARCHAR(4) ,
  Province VARCHAR(50) 
);

SELECT land.c_name, count(berg.land) 
FROM (
  SELECT avg(a.count3) AS avgberg 
  FROM (
    SELECT count(berg.land) as count3 
    FROM berg) AS a
  ) AS b
  INNER JOIN land ON land.code = berg.land
WHERE a.count3 > b.avgberg

运行代码时，我收到错误消息

“错误：表” a“的FROM子句条目丢失
第10行：a.count3> b.avgberg“

Answer 1

我这样理解问题：每个土地上都有许多冰山。查找冰山比平均土地多的土地。可以这样做：

;WITH bergcount AS
(
    SELECT berg.land, count(berg.land) as count3
    FROM berg
    GROUP BY berg.land
)
SELECT land.name, bergcount.count3
FROM bergcount
INNER JOIN land ON land.code = bergcount.land
WHERE bergcount.count3 >
(
    SELECT avg(count3) as avgberg
    FROM bergcount
)

使用您最近发布的新表名，相同的查询将如下所示：

;WITH bergcount AS
(
    SELECT Berg.land, count(Berg.Land) as count3
    FROM Berg
    GROUP BY Berg.land
)
SELECT Land.name, bergcount.count3
FROM bergcount
INNER JOIN Land ON Land.c_namn = bergcount.land
WHERE bergcount.count3 >
(
    SELECT avg(count3) as avgberg
    FROM bergcount
);

Answer 2

您可以使用以下查询获取所需结果。

Select land.name, count(berg.land) 
from land, berg
where land.name = berg.land
group by land.name having count(berg.land) > (SELECT avg(count(berg.land)) as count3 
                                              FROM berg 
                                              group by land) ;

谢谢卡皮尔

SQL：子查询AVG和计数问题

2 个答案: