在mysql中没有匹配条件的情况下获取最新记录

Question

I would like to get latest records even though without matching the conditions in MYsql.

In example, I want to select data on 2013-01-20 by group by product type, but it doesn't match this condition, So it will get the latest date of those product type (2013-01-19 or 2013-01-15).

Coding:

Select date from tblproducttype where 
date=(select max(date) from tblproducttype group by type) where date='2013-01-20'


Table product type

ID  Type  Date
1   2     2013-01-20
2   2     2013-01-20
3   2     2013-01-14
4   3     2013-01-19
5   4     2013-01-16
6   4     2013-01-13

Result should be the following:

ID  Type  Date
1   2     2013-01-20
2   2     2013-01-20
4   3     2013-01-19
5   4     2013-01-16

For results, i want to combine the data for 2013-01-20 with the latest data for other products.

Finally, we can get only latest date of those product type.

How to do that in MYSQL?

Regards.

Answer 1

I think this is what you want:

SELECT p.*
FROM product_type p
JOIN (SELECT Type, MAX(Date) maxdate
      FROM prodct_type
      GROUP BY Type) m
ON p.Type = m.Type and p.Date = m.maxdate

The m subquery finds the latest date for each type. The join then finds all rows for each type on that date.

To filter out a condition, use a HAVING clause in the subquery:

SELECT p.*
FROM product_type p
JOIN (SELECT Type, MAX(Date) maxdate
      FROM prodct_type
      GROUP BY Type
      HAVING maxdate != '2013-01-20') m
ON p.Type = m.Type and p.Date = m.maxdate

or a WHERE clause in the main query:

SELECT p.*
FROM product_type p
JOIN (SELECT Type, MAX(Date) maxdate
      FROM prodct_type
      GROUP BY Type) m
ON p.Type = m.Type and p.Date = m.maxdate
WHERE maxDate != '2013-01-20'

Answer 2

You can do this by aggregating the data to get the maximum date and then joining this information back to the original table:

select t.id, t.type, t.date
from t join
     (select type, max(date) as maxdate
      from t
      group by type
     ) tsum
     on t.type = tsum.type and t.date = tsum.maxdate
order by id;