我不確定我需要什麼類型的連接,因爲我不熟悉嘗試以這種方式覆蓋數據或者如果它是可行的。SQL自然連接POSTGRES
我有兩個表這兩者有着相似的一組數據,並且兩者都涉及到3號的父表通Room_id.
我有一個表稱爲Room_rates存儲的平均價格爲每間客房(ROOM_ID)
+-------+---------+-----------+-------+--------+---------------------------+---------------------------+
| id | room_id | dayofweek | price | source | created_at | updated_at |
+-------+---------+-----------+-------+--------+---------------------------+---------------------------+
| 87936 | 2517 | 0 | 14.58 | 1 | 2010-02-22 17:47:14 +0100 | 2010-02-22 17:47:14 +0100 |
| 87937 | 2517 | 1 | 14.58 | 1 | 2010-02-22 17:47:14 +0100 | 2010-02-22 17:47:14 +0100 |
| 87938 | 2517 | 2 | 14.52 | 1 | 2010-02-22 17:47:14 +0100 | 2010-02-22 17:47:14 +0100 |
| 87939 | 2517 | 3 | 14.52 | 1 | 2010-02-22 17:47:14 +0100 | 2010-02-22 17:47:14 +0100 |
| 87940 | 2517 | 4 | 14.52 | 1 | 2010-02-22 17:47:15 +0100 | 2010-02-22 17:47:15 +0100 |
| 87941 | 2517 | 5 | 14.4 | 1 | 2010-02-22 17:47:15 +0100 | 2010-02-22 17:47:15 +0100 |
| 87942 | 2517 | 6 | 14.63 | 1 | 2010-02-22 17:47:15 +0100 | 2010-02-22 17:47:15 +0100 |
+-------+---------+-----------+-------+--------+---------------------------+---------------------------+
和稱爲可獲取表,有具體日期
+--------+-------+-------+------------+---------+---------------------------+---------------------------+--------+
| id | price | spots | bookdate | room_id | created_at | updated_at | source |
+--------+-------+-------+------------+---------+---------------------------+---------------------------+--------+
| 221389 | 14.3 | 1 | 2010-03-01 | 2517 | 2010-02-21 22:31:06 +0100 | 2010-02-21 22:31:06 +0100 | 1 |
| 221390 | 14.3 | 1 | 2010-03-02 | 2517 | 2010-02-21 22:31:06 +0100 | 2010-02-21 22:31:06 +0100 | 1 |
| 221391 | 14.3 | 1 | 2010-03-03 | 2517 | 2010-02-21 22:31:06 +0100 | 2010-02-21 22:31:06 +0100 | 1 |
| 221392 | 14.3 | 1 | 2010-03-04 | 2517 | 2010-02-21 22:31:06 +0100 | 2010-02-22 17:47:19 +0100 | 1 |
| 221393 | | 0 | 2010-03-05 | 2517 | 2010-02-21 22:31:06 +0100 | 2010-02-22 17:47:19 +0100 | 1 |
| 221394 | | 0 | 2010-03-06 | 2517 | 2010-02-21 22:31:06 +0100 | 2010-02-22 17:47:19 +0100 | 1 |
| 228185 | | 0 | 2010-03-07 | 2517 | 2010-02-22 17:47:19 +0100 | 2010-02-22 17:47:19 +0100 | 1 |
| 228186 | 14.3 | 1 | 2010-03-08 | 2517 | 2010-02-22 17:47:19 +0100 | 2010-02-22 17:47:19 +0100 | 1 |
| 228187 | 14.3 | 1 | 2010-03-09 | 2517 | 2010-02-22 17:47:19 +0100 | 2010-02-22 17:47:19 +0100 | 1 |
| 228188 | 14.3 | 1 | 2010-03-10 | 2517 | 2010-02-22 17:47:19 +0100 | 2010-02-22 17:47:19 +0100 | 1 |
+--------+-------+-------+------------+---------+---------------------------+---------------------------+--------+
率目前我使用兩個單獨的海rch結果,當前爲Availables
特定日期範圍內的數據存在,或者不存在。如果沒有,我只使用Room_rate
平均值進行備份查詢。
我想使用可用的地方它有可用的價格,但不知何故加入Room_rates填補空白,如果價格不可用或可能根本沒有記錄。
我怎麼能做到這一點?