回答編集履歴
4
調整
answer
CHANGED
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@@ -105,6 +105,35 @@
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105
105
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call myproc;
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106
106
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```
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107
107
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108
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+
# 実際にprocedureが発行しているSQL文
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109
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+
上記procedureが発行しているSQL文はこうです
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110
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```SQL
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111
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select
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112
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t1.name as name1,
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113
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t1.price as price1,
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114
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t1.bikou as bikou1,
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115
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t2.name as name1,
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116
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t2.price as price1,
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117
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t2.bikou as bikou1,
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118
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t3.name as name1,
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t3.price as price1,
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120
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t3.bikou as bikou1,
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121
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t4.name as name2,
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122
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t4.price as price2,
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t4.bikou as bikou2
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from
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(select * from tbl as t0 where (select count(*)+1 from tbl where id=t0.id and pid<t0.pid)=1) as t1
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126
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left join
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(select * from tbl as t0 where (select count(*)+1 from tbl where id=t0.id and pid<t0.pid)=2) as t2
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on t1.id=t2.id
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left join
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(select * from tbl as t0 where (select count(*)+1 from tbl where id=t0.id and pid<t0.pid)=3) as t3
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on t1.id=t3.id
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left join
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(select * from tbl as t0 where (select count(*)+1 from tbl where id=t0.id and pid<t0.pid)=4) as t4
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on t1.id=t4.id
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```
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136
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# 結果
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138
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|name1|price1|bikou1|name2|price2|bikou2|name3|price3|bikou3|name4|price4|bikou4|
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|:--|--:|:--|:--|--:|:--|:--|--:|:--|:--|--:|:--|
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3
調整
answer
CHANGED
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@@ -103,4 +103,11 @@
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103
103
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- procedure実行
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104
104
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```SQL
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105
105
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call myproc;
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106
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-
```
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106
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+
```
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107
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+
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# 結果
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|name1|price1|bikou1|name2|price2|bikou2|name3|price3|bikou3|name4|price4|bikou4|
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|:--|--:|:--|:--|--:|:--|:--|--:|:--|:--|--:|:--|
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|あか|100|aa|あお|200|bb|むらさき|600|xx|みずいろ|700|yy|
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|きいろ|300|aa|みどり|400|bb|ちゃいろ|800|zz|NULL|NULL|NULL|
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|おれんじ|500|aa|NULL|NULL|NULL|NULL|NULL|NULL|NULL|NULL|NULL|
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2
procedure
answer
CHANGED
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@@ -37,4 +37,70 @@
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37
37
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on t2.id=t4.id
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38
38
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```
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39
39
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40
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-
これを右方向に自動的に伸ばしていきたいならプロシージャが必要になります。
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40
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これを右方向に自動的に伸ばしていきたいならプロシージャが必要になります。
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41
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+
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42
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# 右方向にどんどん伸ばす
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43
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44
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- 元データ
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45
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```SQL
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46
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create table tbl(
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47
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pid int primary key,
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48
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id int,
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49
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name varchar(10),
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50
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price int,
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51
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bikou varchar(30)
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52
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);
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53
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+
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54
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insert into tbl values
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55
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(1,1,'あか',100,'aa'),
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56
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(2,1,'あお',200,'bb'),
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57
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(3,2,'きいろ',300,'aa'),
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58
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(4,2,'みどり',400,'bb'),
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59
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(5,3,'おれんじ',500,'aa'),
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60
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(6,1,'むらさき',600,'xx'),
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61
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(7,1,'みずいろ',700,'yy'),
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62
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(8,2,'ちゃいろ',800,'zz');
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63
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```
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64
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65
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- procedure作成
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66
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```SQL
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67
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drop procedure if exists myproc;
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68
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delimiter //
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69
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create procedure myproc()
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70
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begin
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71
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select max(cnt) into @max from (
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72
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select id,count(*) cnt from tbl group by id
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73
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) as sub;
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74
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set @sql="select ";
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75
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set @c=1;
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76
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while @c<=@max do
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77
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if @c>1 then
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78
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set @sql=concat(@sql,",");
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79
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end if;
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80
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set @sql=concat(@sql,"t",@c,".name as name",@c,",t",@c,".price as price",@c,",t",@c,".bikou as bikou",@c);
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81
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set @c=@c+1;
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82
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end while;
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83
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set @c=1;
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84
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while @c<=@max do
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85
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if @c=1 then
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86
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set @sql=concat(@sql," from");
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87
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else
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88
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set @sql=concat(@sql," left join");
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89
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end if;
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90
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set @sql=concat(@sql,"(select * from tbl as t0 where (select count(*)+1 from tbl where id=t0.id and pid<t0.pid)=",@c,") as t",@c);
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91
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if @c>1 then
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92
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set @sql=concat(@sql," on t1.id=t",@c,".id");
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93
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end if;
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94
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set @c=@c+1;
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95
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end while;
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96
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prepare stmt from @sql;
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97
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execute stmt;
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98
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end
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99
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//
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100
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delimiter ;
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101
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```
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102
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※procedureは一回作成すればあとはデータが変化してもcallするだけでよいです
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103
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+
- procedure実行
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104
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```SQL
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105
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call myproc;
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106
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```
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1
調整
answer
CHANGED
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@@ -1,2 +1,40 @@
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1
1
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普通にやると同じidに順位が付かないのでどちらがname1/name2なのか確定できないので
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2
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-
命題のような処理は不可能です。
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2
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命題のような処理は不可能です。
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3
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+
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4
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# sample
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5
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無理やりやるならこんな感じ
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6
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- 元データ
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7
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```SQL
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8
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create table tbl(
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9
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pid int primary key,
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10
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id int,
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11
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name varchar(10),
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12
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price int,
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13
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bikou varchar(30)
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14
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);
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15
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insert into tbl values
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16
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(1,1,'あか',100,'aa'),
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17
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(2,1,'あお',200,'bb'),
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18
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(3,2,'きいろ',300,'aa'),
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19
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(4,2,'みどり',400,'bb'),
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20
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(5,3,'おれんじ',500,'aa');
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21
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```
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22
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- 抽出
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23
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```
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24
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select
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25
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t2.name as name1,
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26
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t2.price as price1,
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27
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+
t2.bikou as bikou1,
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28
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+
t4.name as name2,
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29
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t4.price as price2,
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30
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t4.bikou as bikou2
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31
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from (select *
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32
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from tbl as t1
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33
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where (select count(*)+1 from tbl where id=t1.id and pid<t1.pid)=1) as t2
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34
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left join (select *
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35
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from tbl as t3
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36
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where (select count(*)+1 from tbl where id=t3.id and pid<t3.pid)=2) as t4
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37
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+
on t2.id=t4.id
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38
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+
```
|
|
39
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+
|
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40
|
+
これを右方向に自動的に伸ばしていきたいならプロシージャが必要になります。
|