[英]MySQL GROUP BY multiple columns from different tables
我有以下表格布局:
Table Data
+----------+-------------------------+
| Field | Type |
+----------+-------------------------+
| type | enum('type_b','type_a') |
| type_id | int(11) unsigned |
| data | bigint(20) unsigned |
+----------+-------------------------+
Table A and B:
+--------------+------------------+
| Field | Type |
+--------------+------------------+
| id | int(11) unsigned |
| customer_id | int(11) unsigned |
| ... |
+--------------+------------------+
在表格數據中,存在來自某種類型(a或b)的一些測量數據。 現在我想要永遠的客戶兩種類型的數據a和b的總和。
所以,我想:選擇總和,通過a.customer_id,b.customer_id連接a或b並分組。
導致以下查詢:
SELECT sum(d.data) as total
FROM data d, ta, tb
WHERE
(d.type LIKE "type_a" AND d.type_id = ta.id)
OR
(d.type LIKE "type_b" AND d.type_id = tb.id)
GROUP BY ta.customer_id, tb.customer_id;
這不能讓我得到正確的結果......
我嘗試了幾種方法,左連接,加入客戶表和group by customer.id等。是否有人知道我做錯了什么?
感謝名單!
您的查詢
SELECT sum(d.data) as total
FROM data d, ta, tb
WHERE
(d.type LIKE "type_a" AND d.type_id = ta.id)
OR
(d.type LIKE "type_b" AND d.type_id = tb.id)
GROUP BY a.customer_id, b.customer_id;
假設d中只有一條記錄,它是type_a。 ta和tb各有兩條記錄。 d中的記錄與d.type_id=ta.id
中的ta中的一個記錄匹配。 因此,(dx ta)的組合允許任何tb記錄保留在最終結果中。 你會得到一個意想不到的笛卡兒產品。
SELECT x.customer_id, SUM(data) total
FROM
(
SELECT ta.customer_id, d.data
FROM data d JOIN ta
ON (d.type LIKE "type_a" AND d.type_id = ta.id)
UNION ALL
SELECT tb.customer_id, d.data
FROM data d JOIN tb
ON (d.type LIKE "type_b" AND d.type_id = tb.id)
) X
GROUP BY x.customer_id;
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