使用 group by null 指针从 sqlite 获取值 [英] getting values from sqlite using group by null pointer

问题描述

我有一张表，其中有一些重复记录，现在我正在获取记录而不排除重复记录.我想获取除重复之外的所有记录，而从重复数据中我只想要一条记录.就像如果我有三张相同的记录，我只想要一张记录.我的查询就像，这给出了空指针.

I have a table in that I have some duplicate record now I am getting the record without excluding duplicate records. I want to get all record excluding duplicate, and from duplicate data I want only one record. like if I have three same records i want only one record. my query is like,this giving null pointer.

Cursor dCursor=database.rawQuery( "SELECT FROM note_image GROUP BY IDMATCHER",null,null);

如果我想使用 query() 方法得到这个，我该怎么做.我正在使用这种方法获取所有记录.但我只想要所有记录一次.没有出现两次的记录.

and if I want to get this using query() method how can I do that. I am getting all records by using this method. but I want all records only once. without occurrence two time a record.

public Cursor fetchImage(){
    String[] columns = new String[]{DatabaseHelper.NOTE_IMG_ID,DatabaseHelper.NOTE_HD_IMG_PATH,DatabaseHelper.NOTE_IMG_PATH_THUMB,DatabaseHelper.TEMP_IMG_ID};
    Cursor cursor=database.query(DatabaseHelper.TABLE_NOTE_IMAGE,columns,null,null,null,null,null);
    if (cursor!=null){
        cursor.moveToNext();
    }
    return cursor;
}

推荐答案

I done using this query. taken help from above commented link. ` public Cursor fetchImage() {
               Cursor icursor = database.query(true, DatabaseHelper.TABLE_NOTE_IMAGE, new String[]
                        {DatabaseHelper.TEMP_IMG_ID, DatabaseHelper.NOTE_IMG_PATH_THUMB},
                null, null, DatabaseHelper.TEMP_IMG_ID, null, null, null);
        if (icursor != null) {
            icursor.moveToNext();
        }
        return icursor;
    }`

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