使用sqlite进行Android开发:查询结果为';不要是空的
我有一个相当大的查询,在android外部执行时返回数据,而在android内部执行时不返回任何内容使用sqlite进行Android开发:查询结果为';不要是空的,android,sqlite,android-cursor,Android,Sqlite,Android Cursor,我有一个相当大的查询,在android外部执行时返回数据,而在android内部执行时不返回任何内容 我将查询分成几个部分,并确定联合是正确的 我尝试了一组较小的具有相同行为的数据 我已经用不同的硬件和API版本进行了测试 我使用的是带有常量值的rawQuery方法。 此查询旨在替换当前不支持的完整外部联接 SELECT IFNULL(stype, gtype) AS type, IFNULL(sdate, gdate) AS date, IFNULL(sroute, groute) AS
- 我将查询分成几个部分,并确定联合是正确的
- 我尝试了一组较小的具有相同行为的数据
- 我已经用不同的硬件和API版本进行了测试
- 我使用的是带有常量值的rawQuery方法。
SELECT IFNULL(stype, gtype) AS type, IFNULL(sdate, gdate) AS date, IFNULL(sroute, groute) AS route FROM (
SELECT sp.type AS stype, sp.date AS sdate, -1 AS gtype, gp.date AS gdate, sp.route AS sroute, gp.route AS groute
FROM Sensor_Point AS sp LEFT JOIN GPS_Point AS gp ON gp._id IS NULL AND sp.sent=0 AND sp.route=gp.route AND sp.route=1
UNION ALL
SELECT sp.type AS stype, sp.date AS sdate, -1 AS gtype, gp.date AS gdate, sp.route AS sroute, gp.route AS groute
FROM GPS_Point AS gp LEFT JOIN Sensor_Point AS sp ON sp._id IS NULL AND gp.sent=0 AND sp.route=gp.route AND gp.route=1
) WHERE route=1 ORDER BY date ASC LIMIT 255
如有任何提示,将不胜感激
更新:
看起来问题终于出在查询参数上了,如果我这样设置的话:
String[] args = new String[3];
args[0] = args[1] = args[2] = "1";
Cursor data dataBase.rawQuery(SELECT_POINTS, args);
当直接在查询中硬编码值时,它不起作用
Cursor data = dataBase.rawQuery(SELECT_POINTS, null);
在Android数据库API中,所有查询参数都是字符串。 (这是一个可怕的设计错误。) 您的查询对应于:
... AND sp.route='1'
尝试将参数字符串转换回如下数字:
... AND sp.route = CAST(? AS INT)
或者直接将数字输入查询字符串。非常感谢@CL。就是这样!!我首先认为问题与嵌套查询有关,因为子查询在没有任何强制转换的情况下运行良好,但我错了。