1つの列からのみ重複を削除する

Question

だから私はこのようなものを持っています。結果は2つのテーブルへのクエリです。

+------------------+------------------------------------+ 
| character_name | title        | 
+------------------+------------------------------------+ 
| derp    | a         | 
| derp    | b         | 
| derp    | c         | 
| herp    | a         | 
| herp    | b         | 
| herp    | c         | 
+-------------------------------------------------------+ 

と、私はこの

+------------------+------------------------------------+ 
| character_name | title        | 
+------------------+------------------------------------+ 
| derp    | a         | 
|     | b         | 
|     | c         | 
| herp    | a         | 
|     | b         | 
|     | c         | 
+-------------------------------------------------------+ 

をしたい、これは可能ですか？

Answer 1

これはこの意味ですか？

select case when i.rnk = 1 THEN i.character_name ELSE '' END as NAME 
, i.title 
from(
    select * 
    , row_number() over (partition by character_name order by title) as rnk 
    from t1 
) i 
order by i.character_name 

ファーストネームには結果に表示される値1が表示されます。

アップデート - MySQLバージョン：

SET @r_name:=''; 

select name, title FROM (
    select @r_name:=CASE WHEN @r_name = name THEN '' 
    ELSE name 
    END AS name 
    , @r_name:=name 
    , title 
    FROM 
    t1 
) t2 

Answer 2

あなたはそれがユーザー変数のアシストで行うことができます。

SQL：

SET @last_name = ''; 
SELECT 
    IF(switch_name, tbl2.character_name, '') character_name, 
    tbl2.title 
FROM 
    (
    SELECT 
     character_name, 
     title, 
     character_name != @last_name switch_name, 
     @last_name:=character_name 
    FROM 
     tbl 
    ) tbl2; 

結果：

mysql> SELECT character_name, title FROM tbl; 
+----------------+-------+ 
| character_name | title | 
+----------------+-------+ 
| derp   | a  | 
| derp   | b  | 
| derp   | c  | 
| herp   | a  | 
| herp   | b  | 
| herp   | c  | 
+----------------+-------+ 
6 rows in set (0.00 sec) 

mysql> SET @last_name = ''; 
Query OK, 0 rows affected (0.00 sec) 

mysql> 
mysql> SELECT 
    ->  IF(switch_name, tbl2.character_name, '') character_name, 
    ->  tbl2.title 
    -> FROM 
    ->  (
    ->  SELECT 
    ->   character_name, 
    ->   title, 
    ->   character_name != @last_name switch_name, 
    ->   @last_name:=character_name 
    ->  FROM 
    ->   tbl 
    -> ) tbl2; 
+----------------+-------+ 
| character_name | title | 
+----------------+-------+ 
| derp   | a  | 
|    | b  | 
|    | c  | 
| herp   | a  | 
|    | b  | 
|    | c  | 
+----------------+-------+ 
6 rows in set (0.00 sec) 

Answer 3

それはあなたの指定したテーブル

SELECT CASE 
    WHEN character_name ='derp' AND title ='a' THEN 'derp' 
    WHEN character_name ='derp' AND title ='b' THEN '' 
    WHEN character_name ='derp' AND title ='c' THEN '' 
    WHEN character_name ='herp' AND title ='a' THEN 'herp' 
    WHEN character_name ='herp' AND title ='b' THEN '' 
    WHEN character_name ='herp' AND title ='c' THEN '' 
    end as character_name, 
    title 
    from table_name; 

NOTEのために動作します：あなたのデータが動的であるかどうか、その後上記のようにしますあなたの望む結果を得るためにクエリを書き直し/最適化する必要があります。