Question

My result set seems fine except I’m getting additional duplicate results which I want to avoid, here is that case:

I’m using two tables :

order

id|companyname|routeid|orderdate
1 |company1   | 23dsa | 
2 |company1   | 23dsa | 2011-04-28
3 |company1   | 23dsa | 2011-04-05
4 |company2   | 24gcc | 2011-22-05

vehicle

id| vehiclename | routeid
1 | van1        | 23dsa 
2 | van2        | 24gcc 

This is my query 1 :

select t1.companyname, max(t1.orderdate) as orderdate
from order t1, vehicle t2 where t1.routeid=t2.routeid
group by t1.companyname, t1.orderdate
order by t1.id

This is query 2 :

 select t1.companyname, max(t1.orderdate) as orderdate
    from order t1, vehicle t2 where t1.routeid=t2.routeid
    group by t1.companyname, t1.orderdate having count(1) = 1
    order by t1.id

This is my result :

companyname | orderdate
company1    |  
company1    | 2011-04-28
company1    | 2011-04-05
company2    | 2011-22-05

I’d like it to be like this :

companyname | orderdate
company1    | 2011-04-28
company2    | 2011-22-05

I was missing is not null :

select t1.companyname, max(t1.orderdate) as orderdate
    from order t1, vehicle t2 where t1.orderdate is not null and t1.routeid=t2.routeid
    group by t1.companyname, t1.orderdate
    order by t1.id

Answer 1

What about:

SELECT
    companyname, MAX(orderdate) AS orderdate
FROM
    `order`
GROUP BY
    companyname
ORDER BY
    id

And if you need that vehicle stuff in there:

SELECT
    companyname, MAX(orderdate) AS orderdate
FROM
    `order` o, vehicle v
WHERE
    o.routeid=v.routeid
GROUP BY
    companyname
ORDER BY
    o.id