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group by user_name having count(*)>2 實現具備任意2個值的記錄查看全部
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使用關聯方式實現多屬性的查詢查看全部
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如何在子查詢中匹配兩個值？查看全部
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子查詢：這個查詢是另外一個查詢的條件，稱作子查詢。查看全部
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SQL同屬性的多值過濾查看全部
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同一屬性多值過濾查看全部
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多屬性任取其中幾個的查詢例子查看全部
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累進稅問題，階梯函數查看全部
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select a.user_name from user1 a join user1_skills b on b.user_id = a.id where b.skill in ('念經','變化','騰云','浮水',) and b.skill_level>0 group by a.user_name having couint(*)>=2查看全部
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Select a.user_name,b.skill,c.skill,e.skill From user1 a From user1 a Left join user1_skill b on a.id =b.user_id and b.skill='念經' and b.skill level>0 Left join user1_skill c on a.id = c.user_id and c.skill='變化' and c.skill_level>0 Left join user1_skill d on a.id = d.user_id and d.skill = '騰云' and c.skill_level>0 Left join user1_skill e on a.id = e.user_id and e.skill = '浮水' and e.skill_level>0 Where (case when b.skill is not null then 1 else 0 end) +(case when c.skill is not null then 1 else 0 end) +(case when d.skill is not null then 1 else 0 end) +(case when e.skill is not null then 1 else 0 end)>=2;查看全部
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多列過濾的使用場景：查看全部
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select user_name from user1 where id in (select user_id from user_kills); 使用子查詢可以避免由于子查詢中的數據產生的重復。 select a.user_name from user1 a join user_kills b on a.id =b.user_id; 會產生重復記錄 select distinct a.user_name from user1 a join user_kills b on a.id =b.user_id; 使用distinct去除重復記錄查看全部
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內容簡介：查看全部
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將子查詢改為join寫法時要注意表中關系是不是一對多或多對多，這種情況下要對查詢結果使用distinct去重。查看全部
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select a.user_name from user1 a join user1_skills b on b.user_id = a.id where b.skill in ('念經','變化','騰云','浮水',) and b.skill_level>0 group by a.user_name having couint(*)>=2 ;查看全部
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