SQL：在where子句中不同

Question

I have a query that after execution shows:

Name  | LasName | City
-------------------------
John  | Doe     | London
John  | Doe     | Berlin
Martin| Smith   | Paris

Is there anything I can do in the WHERE clause section in order to get just one John Doe, no matter the city?

The query is humongous that's why I'm not posting it in here.

If there's anything you think I can do, please, post a fake query explaining it, I just need to get the concept.

Thanks a lot!

Answer 1

You don't state RDBMS. One way that should work in all.

SELECT Name,
       LasName,
       MAX(City) AS City
FROM   YourQuery
GROUP  BY Name,
          LasName 

You say you don't care which city. This gives you the last alphabetically.

Or an alternative

SELECT Name,
       LasName,
       City
FROM   (SELECT Name,
               LasName,
               City,
               ROW_NUMBER() OVER (PARTITION BY Name, LasName ORDER BY (SELECT 0)) AS RN
        FROM   YourQuery) T
WHERE  RN = 1 

Answer 2

Assuming you're using MySQL and you want to see all the cities for the same user name on one line, try something like:

select Name, LasName, group_concat(City)
from LargeQuery
group by Name, LasName

Answer 3

You can use the following query (t-sql)

SELECT Distinct Name,LasName
FROM TableName

Answer 4

Assuming that you are asking to query just one row, irrespective of the city, try this,

select * from tablename 
where name = 'John'
and lasname = 'Doe'
and rownum = 1;

Answer 5

select * from `TableName` group by Name, LasName