Sqlite3查询在Android上无法正常运行

Question

我有这样的查询

SELECT value1 FROM mytable where (value1 > value2) AND category = 1 ;

这在Android中无法正常执行。虽然如果我手动去

/data/data/packagename/databases/mydatabase.db

这是代码

try {
SQLiteDatabase sqdb = _context.openOrCreateDatabase(_DB_NAME, 0,
                null);
String sql = null;
sql = "SELECT value1 FROM mytable where (value1 > value2) AND category = " + category
                +"; ";
Cursor c = sqdb.rawQuery(sql, null);
Log.i("sql = ", sql);

if (c.moveToFirst()) {
while (!c.isAfterLast()) {

categoryValue = c.getString(0);
c.moveToNext();
}
}
Log.i("categoryValue", categoryValue);
sqdb.close();
c.close();
} catch (Exception e) {
e.printStackTrace();
}

然后执行它。然后它完全正常。

发生了什么事？

Answer 1

我相信首先需要关闭游标，然后关闭数据库连接

//the order should be
c.close();
sqdb.close();