執行順序
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from
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on
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join/pivot/unpivot(mysql沒有pivot和unpivot)
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where
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group by
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having
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select
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distinct
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order by
- limit（oralce沒有）
書寫順序
select distinct <select_list> from <left_table> <join_type>join <right_table> on <join_condition> where <where_condition> group by <group_by_list> having <having_condition> order by <order_by_list> limit
