更新mysql select into插入語句

Question

我有以下表格：

單據

| id  | title             | authors |
-------------------------------------
| 1   | Arms and the Man  |         |
| 2   | East of Eden      |         |
| 3   | If Not Now, When? |         |

作家

| id  | initial | lastname     |
--------------------------------
| 1   | J       | Bloggs       |
| 2   | J       | Doe          |
| 3   | P       | Punchclock   |
| 4   | D       | Botts        |

著作權

| id  | document_id  | author_id |
----------------------------------
| 1   | 1            | 1         |
| 2   | 1            | 2         |
| 3   | 1            | 3         |
| 4   | 2            | 3         |
| 5   | 2            | 4         |
| 6   | 3            | 1         |
| 7   | 3            | 3         |
| 8   | 3            | 4         |

並且我有以下sql語句：

select d.id, d.title, 
group_concat(concat(a.lastname,', ', a.initial, '.') 
             order by a.lastname, a.initial separator ' ') authors
from documents d
inner join authorships ash on ash.document_id = d.id
inner join authors a on ash.author_id = a.id
group by d.id, d.title

返回以下結果：

| id  | title             | authors                             |
-----------------------------------------------------------------
| 1   | Arms and the Man  | Bloggs, J. Doe, J. Punchclock, P.   |
| 2   | East of Eden      | Punchclock, P. Botts, D.            |
| 3   | If Not Now, When? | Bloggs, J. Punchclock, P. Botts, D. |

我需要將select轉換為一條update語句，以使用SQL語句中顯示的結果更新documents表中的authors列。

我猜我需要以某種方式將select語句嵌入更新語句中？ 這是我嘗試過的，盡管不正確：

update p set authors = group_concat(concat(a.lastname,', ', a.initial, '.') 
             order by a.lastname, a.initial separator ' ')
from documents d
inner join authorships ash on ash.document_id = d.id
inner join authors a on ash.author_id = a.id
group by d.id, d.title

Answer 1

我真的建議您使用此“計算數據”創建一個View，如果您確實想在db中擁有這些值，則不要嘗試將此非規范化值放在表中。 如果您不這樣做，則必須創建觸發器以使這些值保持“最新”，並且會使您的生活變得過於復雜。

現在，對於“理論解”

UPDATE documents base_d
inner join
  (select d.id, d.title, 
   group_concat(concat(a.lastname,', ', a.initial, '.') 
             order by a.lastname, a.initial separator ' ') authors
   from documents d
   inner join authorships ash on ash.document_id = d.id
   inner join authors a on ash.author_id = a.id
   group by d.id, d.title) as d1
 on base_d.id = d1.id
 set base_d.authors = d1.authors;

視圖解決方案：

create view v_documents_withAuthors as
(select d.id, d.title, 
group_concat(concat(a.lastname,', ', a.initial, '.') 
             order by a.lastname, a.initial separator ' ') authors
from documents d
inner join authorships ash on ash.document_id = d.id
inner join authors a on ash.author_id = a.id
group by d.id, d.title)

參見SqlFiddle