Android SQLite性能：单个查询中的多个选择在多个查询中单选？

Question

性能方面，哪一个更好（对于单个表）？：

1. 在单个查询中进行多项选择或
2. 在多个查询中单选？

示例：

/*table schema*/
create table ACTIVITY_TABLE (
ID integer primary key autoincrement,
INTERVAL_ID integer not null, 
ACTIVITY_TYPE text , 
WIFI_LIST text, 
COUNT integer not null );



/*Multipe selects in single query*/
select * from 
    (select sum(COUNT)/60 as Physical from ACTIVITY_TABLE where  INTERVAL_ID >=1  and  INTERVAL_ID <=3 and (ACTIVITY_TYPE="Still" or ACTIVITY_TYPE = "Walking" or ACTIVITY_TYPE = "Running"  ) ),
    (select sum(COUNT)/60 as vehicular from ACTIVITY_TABLE where  INTERVAL_ID >=1  and  INTERVAL_ID <=3 and (ACTIVITY_TYPE="InVehicle" ) );

Answer 1

对于您的示例，您可以通过以下方式修改查询，这将更有效，我没有测试查询。

select
sum(case when activitytype='walking' or activitytype='still' or activitytype='running' then COUNT else 0 end )/60 as physical,

sum(case when activitytype='InVehicle' then COUNT else 0 end)/60 as vehicular

from

activity_table

where interval_id>=1 and interval_id<=3