如何仅选择唯一记录

Question

By that I mean leaving any duplicate records

For example

ID  NAME
1   a
2   a
3   b
4   b
5   c

Desired output.

5 c only

I am tired of trying this . So I don't think I don't have any reasonably code to paste here .

Answer 1

Here is one way:

select t.*
from table t
where not exists (select 1
                  from table t2
                  where t2.name = t.name and t2.id <> t.id
                 );

Here is another way:

select t.*
from table t join
     (select name, count(*) as cnt
      from table t
      group by name
      having cnt = 1
     ) tt
     on tt.name = t.name;

Answer 2

这是另一种可能的方法：

select min(id), name from table group by name having count(*) = 1

Answer 3

I think the cleanest way to do this is to select the name and id for each row, group by the name, and filter only on values that have a COUNT(*) of 1. This means any rows that have a name that is not unique are excluded.

It would look like this:

SELECT id, name
FROM myTable
GROUP BY name
HAVING COUNT(*) = 1;

I can't get SQL to work, but verified this in MySQL workbench:

Answer 4

Here is yet another way to do it:

SELECT * FROM table AS A 
   WHERE (SELECT COUNT(*) FROM table AS T 
            WHERE T.NAME = A.NAME) = 1

Answer 5

select a.* 
from table a
left join table b on a.name = b.name and a.id <> b.id
where b.id is null;