Question

我使用此代码检查表格中是否存在行：

public boolean checkIdiomInFavorite(Idiom idiom){
        String query = "SELECT *" +  " from " + IdiomsOpenHelper.TABLE_FAVORITE +
                " where " + IdiomsOpenHelper.COLUMN_FAV_ID + " = ?;";
        Cursor cursor = database.rawQuery(query,new String[] { String.valueOf(idiom.getId()) });
        if(cursor.moveToNext()){
            return true;
        }
        else{ 
            return false;
        }
    }

但我总是得到false 有什么想法吗？

Answer 1

我替换了这个

if(cursor.moveToNext()){
        return true;
    }
    else{ 
        return false;
    }

与

return(cursor.moveToFirst());

Answer 2

更改此查询字符串...

String query = "SELECT *" +  " from " + IdiomsOpenHelper.TABLE_FAVORITE +
            " where " + IdiomsOpenHelper.COLUMN_FAV_ID + " = ?;";

...到...

String query = "SELECT * from " + IdiomsOpenHelper.TABLE_FAVORITE +
            " where " + IdiomsOpenHelper.COLUMN_FAV_ID = " + idiom.getId();

然后改变这一行......

Cursor cursor = database.rawQuery(query,new String[] { String.valueOf(idiom.getId()) });

...到...

Cursor cursor = database.rawQuery(query, null);

Answer 3

使用以下代码：

public boolean checkIdiomInFavorite(Idiom idiom){
        String query = "SELECT *" +  " from " + IdiomsOpenHelper.TABLE_FAVORITE +
                " where " + IdiomsOpenHelper.COLUMN_FAV_ID + " = ?;";
        Cursor cursor = database.rawQuery(query,new String[] { String.valueOf(idiom.getId()) });
        if(cursor.moveToNext()){
            return true;
        }
        else{ 
            return false;
        }
    }

你可以检测到这种尊重吗？我正在使用SELECT *，这意味着所有列...或者使用您在该表中实际拥有的任何列名。

您还可以计算表的总行数以检查它是否返回0 ...如果返回0则不存在数据。

如何检查表中是否存在行？

3 个答案: