Question

我有一条select语句，该语句返回一组ID和一个maxdate。现在，我要使用给定的发票ID的给定的maxdate更新发票表中的performance_date。

Select invoices.id, max(invoicepositions.performance_date) as maxdate
from invoices
inner join invoicepositions on invoices.id = invoicepositions.invoice_id
where invoices.performance_date IS NULL
group by invoices.id

（MySQL）怎么可能？

Answer 1

您可以将当前的SELECT查询用作Derived Table，并使用Join将其invoices到id表中，然后进行更新。

UPDATE invoices AS i 
JOIN
(
  Select invoices.id, max(invoicepositions.performance_date) as maxdate
  from invoices
  inner join invoicepositions on invoices.id = invoicepositions.invoice_id
  where invoices.performance_date IS NULL
  group by invoices.id
) AS dt 
  ON dt.id = i.id 
SET i.performance_date = dt.maxdate

使用maxdate更新行，其中给出了select中的id和select中的maxdate

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