回答編集履歴
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推敲
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@@ -1,4 +1,4 @@
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SQL Serverなら、軸を作って結合するのが
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経験的にSQL Serverなら、軸を作って結合するのが高速です。
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```SQL
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select base.keyword, lt.old_value, gt.new_value
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from (
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修正
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from change_history
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group by keyword
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) base
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inner join change_history lt
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on base.keyword=lt.keyword and base.min_change_at=lt.change_at
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inner join change_history gt
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on base.keyword=gt.keyword and base.max_change_at=gt.change_at
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```
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