android 开发，MediaStore去重查询，使用Group By

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String[] projection = {

MediaStore.Images.ImageColumns._ID,

MediaStore.Images.ImageColumns.DATA,

"(SELECT _data FROM thumbnails WHERE thumbnails.image_id =images._id) AS thumbnail",

};

String selection = "0==0) GROUP BY (bucket_display_name";

Uri uri = MediaStore.Images.Media.getContentUri("external");

Cursor c = MediaStore.Images.Media.query(this.getContentResolver(), uri, projection, selection, null,"_id");

while(c.moveToNext()) {

Log.i("zhangrl", ""+c.getLong(c.getColumnIndexOrThrow("_id"))

+ "|" + c.getString(c.getColumnIndexOrThrow("_data"))

+ "|" + c.getString(c.getColumnIndexOrThrow("thumbnail"))

);

}

只需用在Selection出加上

String selection = "0==0) GROUP BY (bucket_display_name";

Android会将query中的参数整合成一条sql语句，

其中会将selection的字符串自动加一对括号，

变成“WHERE （XXX）”的形式，

所以要特别注意selection中有括号的情况