AVG(COLUMN_SCORE) 不生成平均值

Question

在我的应用程序中。我有一系列的表格。

• 联赛
• 投球手
• 系列
• 游戏

当投球手输入他/她的分数时，id 可能看起来像这样；

• 联赛 ID = 2
• 投球手 id = 1
• 系列 id = 1
• 游戏 ID = 1,2,3

在我的游戏表中，我记录了每场比赛的得分（即 1、2、3）。我希望能够生成一个系列的平均分数（即 1）。

我知道这可以用

CREATE VIEW AVERAGE_SCORE AS SELECT AVG(COLUMN_SCORE) FROMFROM " + Game.TABLE_NAME + " WHERE " + Game.COLUMN_LEAGUE_ID + " = '" + leagueId + "'" + " AND " + Game.COLUMN_BOWLER_ID + " = '" + bowlerId + "'" + " AND " + Game.COLUMN_SERIES_ID + " = '" + seriesId + "'" + " ORDER BY " +
        Game.COLUMN_TIMESTAMP + " DESC";

我已设法使用以下代码在 logcat 中显示一个值：

public int getSeriesAverage(String leagueId, String bowlerId, String seriesId)
    {
        int total = 0;
        SQLiteDatabase database = getReadableDatabase();
        Cursor cursor = database.rawQuery("CREATE VIEW IF NOT EXISTS AVERAGE_SCORE AS SELECT AVG(COLUMN_SCORE) FROM " + Game.TABLE_NAME + " WHERE " + Game.COLUMN_LEAGUE_ID + " = '" + leagueId + "'" + " AND " + Game.COLUMN_BOWLER_ID + " = '" + bowlerId + "'" + " AND " + Game.COLUMN_SERIES_ID + " = '" + seriesId + "'" + " ORDER BY " +
                Game.COLUMN_TIMESTAMP + " DESC", null);
        if (cursor.moveToFirst()) {
            do {
            total = cursor.getInt(0);
        }while (cursor.moveToNext());
        }
        cursor.close();
        //Close Database Connection
        database.close();
        Log.d("GET AVERAGE FROM SQL","Average = >>>>" + total + "<<<<");
        return total;
    }

但是，它似乎没有生成平均值。在我的数据库中，我有三个分数 Game 1 = 222、Game 2 = 300、Game 3 = 200。平均值应该是 240。但 Log.d 显示为 0。

07-24 19:58:53.385 7287-7287/ca.rvogl.tpbcui D/GET AVERAGE FROM SQL: Average = >>>>0<<<<

我做错了什么，任何帮助将不胜感激

更改代码：

public int getSeriesAverage(String leagueId, String bowlerId, String seriesId)
    {
        int total = 0;
        SQLiteDatabase database = getReadableDatabase();
        Cursor cursor = database.rawQuery("SELECT AVG(COLUMN_SCORE) FROM " + Game.TABLE_NAME + " WHERE " + Game.COLUMN_LEAGUE_ID + " = '" + leagueId + "'" + " AND " + Game.COLUMN_BOWLER_ID + " = '" + bowlerId + "'" + " AND " + Game.COLUMN_SERIES_ID + " = '" + seriesId + "'", null);
        if (cursor.moveToFirst()) {
            do {
            total = cursor.getInt(0);
        }while (cursor.moveToNext());
        }
        cursor.close();
        //Close Database Connection
        database.close();
        Log.d("GET AVERAGE FROM SQL","Average = >>>>" + total + "<<<<");
        return total;
    }

系列类：

public class Series {

    public static final String TABLE_NAME = "Series";

    public static final String COLUMN_ID = "_id";
    public static final String COLUMN_LEAGUE_ID = "league_id";
    public static final String COLUMN_BOWLER_ID = "bowler_id";
    public static final String COLUMN_NAME = "name";
    public static final String COLUMN_SERIES_AVERAGE = "average";
    public static final String COLUMN_TIMESTAMP = "timestamp";

    private int id;
    private String league_id;
    private String bowler_id;
    private String name;
    private String average;
    private String timestamp;


    // Create table SQL query
    public static final String CREATE_TABLE =
            "CREATE TABLE " + TABLE_NAME + "("
                    + COLUMN_ID + " INTEGER PRIMARY KEY AUTOINCREMENT,"
                    + COLUMN_LEAGUE_ID + " TEXT,"
                    + COLUMN_BOWLER_ID + " TEXT,"
                    + COLUMN_NAME + " TEXT,"
                    + COLUMN_SERIES_AVERAGE + " TEXT,"
                    + COLUMN_TIMESTAMP + " DATETIME DEFAULT CURRENT_TIMESTAMP"
                    + ")";

    public Series() {
    }

    public Series(int id, String league_id, String bowler_id, String name, String average, String timestamp) {
        this.id = id;
        this.league_id = league_id;
        this.bowler_id = bowler_id;
        this.name = name;
        this.average = average;
        this.timestamp = timestamp;
    }

    public int getId() {
        return id;
    }

    public String getLeagueId() {return league_id;}

    public String getBowlerId() {return bowler_id;}

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public String getAverage() {
        return average;
    }

    public void setAverage(String average) {
        this.average = average;
    }

    public String getTimestamp() {
        return timestamp;
    }

    public void setId(int id) {
        this.id = id;
    }

    public void setLeagueId(String league_id) {
        this.league_id = league_id;
    }

    public void setBowlerId(String bowler_id) {
        this.bowler_id = bowler_id;
    }

    public void setTimestamp(String timestamp) {
        this.timestamp = timestamp;
    }
}

更新方法：

 public int getSeriesAverage(String leagueId, String bowlerId, String seriesId)
    {
        int total = 0;
        SQLiteDatabase database = getReadableDatabase();
        Cursor cursor = database.rawQuery("SELECT AVG(" + Game.COLUMN_SCORE + ") FROM " + Game.TABLE_NAME + " WHERE " + Game.COLUMN_LEAGUE_ID + " = '" + leagueId + "'" + " AND " + Game.COLUMN_BOWLER_ID + " = '" + bowlerId + "'" + " AND " + Game.COLUMN_SERIES_ID + " = '" + seriesId + "'", null);
        if (cursor.moveToFirst()) {
            do {
            total = cursor.getInt(0);
        }while (cursor.moveToNext());
        }
        cursor.close();
        //Close Database Connection
        database.close();
        Log.d("GET AVERAGE FROM SQL","Average = >>>>" + total + "<<<<");
        ContentValues values = new ContentValues();
        values.put(Series.COLUMN_SERIES_AVERAGE,Series.getAverage());
        Log.d("GET AVERAGE FROM SQL","Average = >>>>" + Series.COLUMN_SERIES_AVERAGE + "<<<<");
        return total;
    }

Answer 1

您的 sql 语句是 CREATE 语句，而不是获取行的查询。所以改变它：

"SELECT AVG(" + Game.COLUMN_SCORE + ") FROM " + Game.TABLE_NAME + " WHERE " + Game.COLUMN_LEAGUE_ID + " = '" + leagueId + "'" + " AND " + Game.COLUMN_BOWLER_ID + " = '" + bowlerId + "'" + " AND " + Game.COLUMN_SERIES_ID + " = '" + seriesId + "'"

您可能还需要更改：total = cursor.getInt(0);
我不确定将产生的平均值是否会四舍五入为int。
最好使用getDouble 或getString 然后解析为int