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仅使用SQL(MySQL)我想选择父子关系的最后一个子行,其中子行按时间戳排序.
例如,使用表发票和invoice_items,我想分别为每个发票的最新(即：最近时间戳)invoice_items记录.
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|Invoices |
--------------------------
|invoice_id| other fields|
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| 1 | ... |
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| 2 | ... |
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| 3 | ... |
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|Invoice_Items |
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| id | invoice_id | invoice_item_timestamp |
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| 1 | 1 | 2009-12-01 10:00:00 |
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| 2 | 1 | 2009-12-01 10:01:00 |
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| 3 | 1 | 2009-12-01 10:02:00 |
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| 4 | 2 | 2009-12-01 9:00:00 |
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| 5 | 3 | 2009-12-02 08:30:00 |
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| 6 | 3 | 2009-12-03 08:31:00 |
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生成结果集的最佳SQL语法是什么,看起来像下表？
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|invoice_id| invoice_item_id |invoice_item_timestamp|
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| 1 | 3 | 2009-12-01 10:02:00 |
| 2 | 4 | 2009-12-01 09:00:00 |
| 3 | 6 | 2009-12-03 08:31:00 |
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最佳答案
SELECT i.*,it.*
FROM invoices i
INNER JOIN (
SELECT invoice_id,MAX(invoice_item_timestamp)
FROM invoice_items
GROUP BY invoice_id
) it ON (i.invoice_id=it.invoice_id)
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