mysql多表选择最近7天

我有3个表，其中包含一些有日期和数值的记录（这些表不能合并）。我想用表格中的信息制作一个条形图。条形图按天分组，应显示最近七天

之前我有两个表，并使用了以下查询方案：

SELECT
    t.credits1,
    t.credits2,
    t.date
FROM
    (
        (
            SELECT
                t1.credits1,
                t2.credits2,
                t1.date
            FROM
                (
                    SELECT
                        SUM(credits) AS credits1,
                        date
                    FROM
                        table1
                    WHERE
                        table1.date >= DATE_SUB(CURDATE(), INTERVAL 7 DAY)
                    GROUP BY
                        DATE(table1.date)
                ) t1

                LEFT JOIN
                (
                    SELECT
                        SUM(credits) AS credits2,
                        date
                    FROM
                        table2
                    WHERE
                        table2.date >= DATE_SUB(CURDATE(), INTERVAL 7 DAY)
                    GROUP BY
                        DATE(table2.date)
                ) t2
                ON t1.date = t2.date
        )
        UNION
        (
            SELECT
                t1.credits1,
                t2.credits2,
                t1.date
            FROM
                (
                    SELECT
                        SUM(credits) AS credits1,
                        date
                    FROM
                        table1
                    WHERE
                        table1.date >= DATE_SUB(CURDATE(), INTERVAL 7 DAY)
                    GROUP BY
                        DATE(table1.date)
                ) t1

                RIGHT JOIN
                (
                    SELECT
                        SUM(credits) AS credits2,
                        date
                    FROM
                        table2
                    WHERE
                        table2.date >= DATE_SUB(CURDATE(), INTERVAL 7 DAY)
                    GROUP BY
                        DATE(table2.date)
                ) t2
                ON t1.date = t2.date
        )
    ) t GROUP BY
DATE(date)

（伪代码）

但是我怎么能用两张以上的桌子做到这一点呢？ 是否有机会将过去7天的日期设置为基准，以便我每次获得7张记录

---

指出问题：如果一天内第一个表中没有记录，我将无法从其他表中获取当天的记录。

我假设这三个表具有相似的模式？尝试使用UNION ALL将表连接在一起

SELECT ABB1.date, SUM(ABB1.credit) AS daily_total
FROM
    (SELECT date, credits
    FROM table1

    UNION ALL 

    SELECT date, credits
    FROM table1

    UNION ALL 

    SELECT date, credits
    FROM table2) AS ABB1
WHERE DATE >= DATE_SUB(CURDATE(), INTERVAL 7 DAY)