android - android中的sqlite聚合max(sum())错误

Question

我正在尝试执行下面的查询，但我误用了聚合函数 sum()

查询

select max(sum(entry.amount)),category.name from entry,category where entry.amount<0 and entry.cid=category.cid group by category.name  

LogCat 输出

android.database.sqlite.SQLiteException: misuse of aggregate function sum() (code 1): , while  compiling: select sum(entry.amount),category.name from entry,category where entry.amount<0 and  entry.cid=category.cid group by category.name 09-22 20:20:18.626: E/AndroidRuntime(4093):    at android.database.sqlite.SQLiteConnection.nativePrepareStatement(Native Method)

有什么建议吗？问候，哥

Answer 1

您不能在单个查询中两次聚合值，但这可以通过子查询解决。

尝试:

select max(amountsum)
from (select sum(entry.amount) as amountsum
      from entry,category
      where entry.amount<0
        and entry.cid=category.cid
      group by category.name)

注释:

• 未经测试

• 不确定查询的逻辑:您正在聚合值以便只保留一个条目，因此查询 category.name 没有意义