質問編集履歴
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誤字
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SELECT * FROM PRODUCT_MST PM
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INNER JOIN PRODUCT_MST_DTL ON PM.PM_ID = PMD.PM_ID AND PM.DEL_FLG = 0
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INNER JOIN PRODUCT_MST_DTL PMD ON PM.PM_ID = PMD.PM_ID AND PM.DEL_FLG = 0
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```
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SELECT * FROM PRODUCT_MST PM
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INNER JOIN PRODUCT_MST_DTL ON PM.PM_ID = PMD.PM_ID
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INNER JOIN PRODUCT_MST_DTL PMD ON PM.PM_ID = PMD.PM_ID
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WHERE PM.DEL_FLG = 0
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INNER JOINでは結果が同じというのをネットでちらほら見ましたが
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大量データを扱った際にパフォーマンス的には違いがでるのでしょうか？
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たとえば、
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```SQL
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SELECT * FROM PRODUCT_MST PM
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INNER JOIN PRODUCT_MST_DTL ON PM.PM_ID = PMD.PM_ID AND PM.DEL_FLG = 0
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```
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というＳＱＬと
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```SQL
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SELECT * FROM PRODUCT_MST PM
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INNER JOIN PRODUCT_MST_DTL ON PM.PM_ID = PMD.PM_ID
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WHERE PM.DEL_FLG = 0
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```
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というＳＱＬではパフォーマンスに明確な差がでますでしょうか？
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個人的には前者の方が、結合するテーブルを絞り込んでいるのでパフォーマンスが良さそうに見えるのですが・・。
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