回答編集履歴
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sample
answer
CHANGED
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@@ -5,4 +5,55 @@
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5
5
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GROUP BY first_name_kana,last_name_kana,phone_number,city
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6
6
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HAVING count(*)>1
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7
7
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```
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8
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-
とするだけでよいかと思います
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8
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とするだけでよいかと思います
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9
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+
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10
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# sample
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11
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12
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```SQL
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13
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create table nayose_otameshi(id int primary key auto_increment,
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first_name_kana varchar(10),
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15
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last_name_kana varchar(10),
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phone_number varchar(10),
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city varchar(10));
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insert into nayose_otameshi(first_name_kana,last_name_kana,phone_number,city) values
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('f1','l1','p1','c1'),
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21
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('f2','l2','p2','c2'),
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('f2','l2','p2','c2'),
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('f3','l3','p3','c3'),
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('f1','l4','p4','c4'),
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('f1','l1','p1','c1'),
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('f3','l3','p3','c3'),
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('f2','l2','p2','c2');
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```
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29
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上記のように別途主キーが設定されているのであれば２番め以降に出て来るレコードはこう
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```SQL
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select id from nayose_otameshi as t1
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where exists(select 1 from nayose_otameshi as t2
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where 1
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and t1.first_name_kana=t2.first_name_kana
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and t1.last_name_kana=t2.last_name_kana
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and t1.phone_number=t2.phone_number
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and t1.city=t2.city
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and t1.id>t2.id
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)
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```
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id=3,6,7,8が抽出されるのでこれを利用して削除
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```SQL
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delete from nayose_otameshi
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where id in(
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select id from(
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select id from nayose_otameshi as t1
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where exists(select 1 from nayose_otameshi as t2
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where 1
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and t1.first_name_kana=t2.first_name_kana
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and t1.last_name_kana=t2.last_name_kana
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and t1.phone_number=t2.phone_number
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and t1.city=t2.city
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and t1.id>t2.id
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)
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55
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)as temp
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)
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```
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58
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deleteに自己結合したデータはダイレクトにつかえないので
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59
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一度ダミーのサブクエリでselectを抽出しないといけません
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