显示所有具有相同值大于 1 的分组值

Question

我有table这样的

table1

| ID  |  Val |  Val2  |
|  2  |  AA  |   0    |
|  3  |  AA  |   1    |
|  4  |  AD  |   0    |
|  5  |  CV  |   1    |
|  6  |  AF  |   1    |
|  7  |  CV  |   1    |

我想知道 Val 列中的重复值是否不止一个。我使用了 group by 子句。另外我想知道有多少重复出现在 Val

select Val,count(Val) from table 
group by Val where 
having count(val) > 1

结果：

| Val | count(val) |
| AA  |   2        | 
| CV  |   2        |

现在我想知道哪一列有重复值，所以我使用了 Group_concat 这样的查询

select Val,count(Val), group_concat(ID) from table1 
group by Val where 
having count(val) > 1

结果

| Val | count(val) | group_concat(ID) |
| AA  |   2        |  2,3             |
| CV  |   2        |  5,7             |

现在我不知道如何显示所有重复值，我只通过 group_concat() 显示哪个 ID 具有重复值，但没有 group_concat 列我无法显示所有数据.我尝试使用 Field_in_set 但它似乎不起作用。

select Val,count(Val), group_concat(ID) from table1 
where FIELD_IN_SET(ID,group_concat(ID))
group by Val where 
having count(val) > 1

我希望在 group by 和 count 之后显示所有重复值，如下所示 table

| ID  |  Val |  Val2  |
|  2  |  AA  |   0    |
|  3  |  AA  |   1    |
|  5  |  CV  |   1    |
|  7  |  CV  |   1    |

Answer 1

CREATE TABLE table1 (
  `ID` INTEGER,
  `Val` VARCHAR(2),
  `Val2` INTEGER
);

INSERT INTO table1
  (`ID`, `Val`, `Val2`)
VALUES
  ('2', 'AA', '0'),
  ('3', 'AA', '1'),
  ('4', 'AD', '0'),
  ('5', 'CV', '1'),
  ('6', 'AF', '1'),
  ('7', 'CV', '1');

SELECT  t1.* 
FROM table1 t1 
  INNER JOIN (SELECT COUNT(`Val`) countval, `Val`  FROM table1 GROUP BY `Val`) t2 
    ON t1.`Val` = t2.`Val`
WHERE countval > 1

ID | Val | Val2
-: | :-- | ---:
 2 | AA  |    0
 3 | AA  |    1
 5 | CV  |    1
 7 | CV  |    1

SELECT `ID`, `Val`, `Val2`     
FROM ( SELECT
         `ID`, `Val`, `Val2`,
         COUNT(`Val`) OVER(PARTITION BY `Val`) c1
       FROM table1) t1
   WHERE c1 > 1

ID | Val | Val2
-: | :-- | ---:
 2 | AA  |    0
 3 | AA  |    1
 5 | CV  |    1
 7 | CV  |    1

db<>fiddle here

Answer 2

如果您想 return 具有重复 Val 的行，则使用 EXISTS:

select t.* from tablename t 
where exists (select 1 from tablename where Val = t.Val and ID <> t.ID)

参见demo。
结果：

| ID  | Val | Val2 |
| --- | --- | ---- |
| 2   | AA  | 0    |
| 3   | AA  | 1    |
| 5   | CV  | 1    |
| 7   | CV  | 1    |

显示所有具有相同值大于 1 的分组值

Show all the groupped value that have same value more than 1

mysql

group-by

having