使用sqlite进行Android开发：查询结果不应为空

Question

我有一个相当大的查询，它在android外部执行时返回数据，而在android中执行时没有返回任何内容。

• 我将查询分成几部分并确定联合没问题。
• 我尝试了一组具有相同行为的较小数据。
• 我已经使用不同的硬件和API版本进行了测试。
• 我正在使用带有常量值的rawQuery方法。 http://developer.android.com/reference/android/database/sqlite/SQLiteDatabase.html#rawQuery(java.lang.String, java.lang.String[])

此查询旨在替换当前不支持的FULL OUTER JOIN。

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

任何提示都将不胜感激。

更新

看起来像问题最终是查询参数，如果我这样设置：

String[] args = new String[3];
args[0] = args[1] = args[2] = "1"; 
Cursor data dataBase.rawQuery(SELECT_POINTS, args);

它不起作用，而它直接在查询中硬编码值时起作用。

Cursor data = dataBase.rawQuery(SELECT_POINTS, null);

Answer 1

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)

或者只是将数字直接放入查询字符串中。