mysql在不同条件下从另一个表加入列

Question

我有一张'价格表'。我试图从另一个名为'rate_cycles'的表中加入一个列new_rate，它应该基于某些条件。我在创建这样的查询时遇到了麻烦。 价目表包含前缀，以下是两个表的样本。如果来自价格表的一对国家+地区匹配，我将从周期加入'new_rate'。

如果（在循环表中）前缀为空并通知0我需要从该行加入“new_rate”。如果通知（通知= 1），我需要查找（如果存在）下一行通知为0.如果在该行中前缀为null，则我从该行加入new_rate，但如果前缀不为null则为new_rate值我需要前缀为null并且通知为1的最后一行（如果存在，则为否则为null）。

我怎么能实现这个目标？感谢。

价目表

+----+--------------+---------+--------------+---------+-----------+----------+-----------+----------+--------+---------------------+----------------+
| id | pricelist_id | country | region       | prefix  | is_mobile | is_fixed | is_custom | currency | rate   | last_updated        | has_rate_cycle |
+----+--------------+---------+--------------+---------+-----------+----------+-----------+----------+--------+---------------------+----------------+
|  2 |            1 | Albania | Fixed ALBTEL | 3554249 |         0 |        0 |         0 | USD      | 0.0000 | 2014-09-23 09:48:00 |              1 |
|  3 |            1 | Albania | Fixed ALBTEL | 3554250 |         0 |        0 |         0 | USD      | 0.0000 | 2014-09-23 09:48:00 |              1 |
|  4 |            1 | Albania | Fixed ALBTEL | 3554251 |         0 |        0 |         0 | USD      | 0.0000 | 2014-09-23 09:48:00 |              1 |
|  5 |            1 | Albania | Fixed ALBTEL | 3554252 |         0 |        0 |         0 | USD      | 0.0000 | 2014-09-23 09:48:00 |              1 |
+----+--------------+---------+--------------+---------+-----------+----------+-----------+----------+--------+---------------------+----------------+

周期表

+----+------------+---------+--------------+----------+---------------------+---------------+---------+----------+---------+
| id | carrier_id | country | region       | new_rate | activation_date     | update_status | prefix  | notified | grouped |
+----+------------+---------+--------------+----------+---------------------+---------------+---------+----------+---------+
|  1 |         15 | Albania | Fixed ALBTEL |   1.0000 | 2014-09-30 03:48:00 | NEW           | NULL    |        0 |       0 |
|  2 |         15 | Albania | Fixed ALBTEL |   2.0000 | 2014-10-01 03:48:00 | BLOCKED       | 3554250 |        0 |       0 |
|  3 |         15 | Albania | Fixed ALBTEL |   3.0000 | 2014-10-02 03:48:00 | DECREASE      | NULL    |        0 |       0 |
|  4 |         15 | Albania | Fixed ALBTEL |   4.0000 | 2014-10-03 03:48:00 | NEW           | 3554250 |        0 |       0 |
+----+------------+---------+--------------+----------+---------------------+---------------+---------+----------+---------+

Answer 1

这是一个艰难的查询，并设法使它做我需要的。如果它可以简化一点，它会很棒。我正在分享我的解决方案。

SELECT p.id,p.country, p.region, p.prefix, p.currency, p.rate,

    (SELECT CASE WHEN notified = 0

    THEN    (SELECT CASE WHEN prefix IS NULL
        THEN new_rate
        ELSE    (SELECT CASE WHEN COUNT(new_rate)>0
                THEN (SELECT new_rate FROM pricelist_rates_cycle WHERE country=p.country and region=p.region and notified=1 and prefix is null order by DATE(activation_date) DESC LIMIT 1)
                ELSE NULL
                END
                FROM pricelist_rates_cycle WHERE country=p.country and region=p.region and notified=1 and prefix is null
                )
        END
        FROM pricelist_rates_cycle WHERE country=p.country and region=p.region and notified=0 LIMIT 1)

    ELSE (
            SELECT CASE WHEN COUNT(new_rate)>0
            THEN IF( prefix is null, new_rate,
                    (SELECT new_rate FROM pricelist_rates_cycle WHERE country=p.country and region=p.region and notified=1 and prefix is null order by DATE(activation_date) DESC LIMIT 1)
                    )
            ELSE (SELECT new_rate FROM pricelist_rates_cycle WHERE country=p.country and region=p.region and notified=1 and prefix is null order by DATE(activation_date) DESC LIMIT 1)
            END
            FROM pricelist_rates_cycle WHERE country=p.country and region=p.region and notified=0
         )
    END
    FROM pricelist_rates_cycle WHERE country=p.country and region=p.region LIMIT 1) AS new_rate

FROM pricelist_15 AS p ORDER BY country, region ASC