合并两个 sqldf 语句

Question

我已经试了一整天了。有人可以帮我结合以下查询。我在下面得到了想要的结果，但我知道应该一次完成。

moo<-sqldf('SELECT id, count(id) AS idcount 
           FROM MyData WHERE id IS not null 
           GROUP BY id')
sqldf("SELECT id, idcount  FROM moo 
       WHERE idcount = (SELECT min(idcount) FROM moo)")

Answer 1

答案将取决于接收 SQL 的数据库，没有 with 您必须重复 "moo" 查询

  SELECT id, idcount  
  FROM (
       SELECT id, count(id) AS idcount 
       FROM MyData WHERE id IS NOT NULL 
       GROUP BY id 
       ) moo 
  WHERE idcount = (
    SELECT min(idcount) 
    FROM (
       SELECT id, count(id) AS idcount 
       FROM MyData WHERE id IS NOT NULL 
       GROUP BY id 
       ) 
  OR idcount = (
    SELECT max(idcount) 
    FROM (
       SELECT id, count(id) AS idcount 
       FROM MyData WHERE id IS NOT NULL 
       GROUP BY id 
       )

在代码中这样做可能比在 SQL

中更好

如果 dbms 确实支持 WITH，那么：

  WITH moo AS (  
  SELECT id, idcount  
  FROM (
       SELECT id, count(id) AS idcount 
       FROM MyData WHERE id IS NOT NULL 
       GROUP BY id 
       ) 
    )
  SELECT id, idcount  
  FROM moo
  WHERE idcount = (
    SELECT min(idcount) 
    FROM moo)
  OR idcount = (
    SELECT max(idcount) 
    FROM moo)

合并两个 sqldf 语句

combining two sqldf statements

sql

sqlite

subquery

sqldf