Question

我正在使用Android SQLite（使用Galaxy s2进行测试）我无法解决这个问题

我有一个这样的数据库：

COORDINATES
id latitude   longitude
1  37.996163  -116.644592
2  37.996163  -116.644592
3  37.957507  -116.67467
4  36.370157  -91.156311

我运行查询：

select CAST((latitude*10) AS UNSIGNED) AS lat, CAST((longitude*10) AS UNSIGNED) AS lon from coordinates group by lat,lon

我期待：

lat  lon
379  -1166
363  -911

相反，我得到：

lat  lon
379  -1166
379  -1166
363  -911

对未经CAST修改的值执行“group by” 我做错了什么？对mysql的相同查询工作正常。

感谢

Answer 1

试试这个，我不确定这是否会起作用，但我知道select子句中的更改不适用于where，group ...所以试试这个

select CAST((latitude*10) AS UNSIGNED) AS lat, CAST((longitude*10) AS UNSIGNED) AS lon
from coordinates 
group by CAST((latitude*10) AS UNSIGNED), CAST((longitude*10) AS UNSIGNED)

Answer 2

sqlite没有UNSIGNED数据类型，并且向它投射并没有真正做任何事情。这些值是浮点数，直到您调用例如Cursor getInt()将它们转换为整数。

投射至例如INTEGER代替：

sqlite> create table coordinates(id integer primary key, latitude, longitude);
sqlite> insert into coordinates values(1,37.996163,-116.644592),(2,37.996163,-116.644592),(3,37.957507,-116.67467),(4,36.370157,-91.156311);
sqlite> .head on
sqlite> select CAST((latitude*10) AS UNSIGNED) AS lat, CAST((longitude*10) AS UNSIGNED) AS lon from coordinates group by lat,lon;
lat|lon
363.70157|-911.56311
379.57507|-1166.7467
379.96163|-1166.44592
sqlite> select CAST((latitude*10) AS INTEGER) AS lat, CAST((longitude*10) AS INTEGER) AS lon from coordinates group by lat,lon;
lat|lon
363|-911
379|-1166
sqlite>

sqLite - 带有CAST的已修改列中的GROUP BY

2 个答案: