android - 在 SQLite 中选择有限制的随机行

Question

我经历了很多相关的话题，但我还没有成功。

我不知道哪里出错了，我有以下方法来获取行。

    public Cursor getallrows (String fid , String sid , String bid , String pid , String limit)
    {
        return db.query(DATABASE_ALLPENLIST, new String[] {"rowpos","Peninnerid","issampled","onesymbol","twosymbol","threesymbol","foursymbol","fivesymbol","buildingid","farmid","sampleid","penid"}, "farmid = "+fid+" and sampleid = "+sid+" and buildingid = "+bid+" and penid = "+pid , null, null, null,"RANDOM()",limit);
    }

但上述方法返回限制中提到的正确行数但不是随机顺序，它返回限制变量中提到的前 n 行。

RANDOM() 区分大小写吗？但我也尝试用 Random() 和 "RANDOM() LIMIT "+limit 代替第 7 个参数。

提前致谢。

Answer 1

如果 limit 变量是字符串类型，这个查询应该返回随机行，或者你可以像这样明确地使用它:

db.query(DATABASE_ALLPENLIST, 
         new String[] {"rowpos","Peninnerid","issampled","onesymbol","twosymbol","threesymbol","foursymbol","fivesymbol","buildingid","farmid","sampleid","penid"}, 
         "farmid = "+fid+" and sampleid = "+sid+" and buildingid = "+bid+" and penid = "+pid ,
         null, 
         null, 
         null,
         "RANDOM()",
         "1");

或尝试原始查询:

db.rawQuery("Select rowpos, Peninnerid , issampled, onesymbol, twosymbol, threesymbol, foursymbol, fivesymbol, buildingid, farmid, sampleid, penid From " + DATABASE_ALLPENLIST + " Order By RANDOM() LIMIT ?", new String[] {limit});

此 API 的文档:Link