如何在MySQL中的2条记录中选择最后一个日期

Question

How to select last date in 2 records in Mysql ?

TABLE A

SID NAME Sex
1  Jam  M
2  Da   F

TABLE B

 ID Title SID Date
   1  A     1   2012-07-31 09:57:10
   2  NULL  1   2012-07-31 09:57:13
   3  A     2   2012-07-31 10:10:13
   4  NULL  2   2012-07-31 10:57:13

I want to inner join those two tables,

but select only one record only of Table B(distinct of SID) where title not null then show the

biggest Date of title is null field.

Result want the biggest Date of Null title:

ID Name Title SID  Date
1  Jam  A     1    **2012-07-31 09:57:13**
2  DA   A     2    **2012-07-31 10:57:13**

How to do that ?

Answer 1

I think something like this will work for you:

SELECT b.ID, a.NAME, b.Title, b.SID, b.Date
FROM TABLEA a
    INNER JOIN (SELECT SID, IFNULL(Title, "") AS Title,
                       MAX(IF(Title IS NULL, Date, NULL)) Date
                FROM TABLEB GROUP BY SID) b
        ON a.SID = b,SID;

Answer 2

SELECT b.ID, a.NAME, b.Title, b.SID, b.Datea 
from tablea a left outer join 
  (( SELECT sid, MAX(datea) AS latest
         FROM tableb
          where title is not null 
          GROUP BY sid) AS dt
INNER JOIN tableb b  ON b.sid= dt.sid  and b.datea=dt.latest )
on a.sid=b.sid

Answer 3

Try my code (it works):

SELECT b.id, b.title, b.sid, b.date 
    FROM table_b as b 
    JOIN table_a as a ON a.sid = b.sid
    WHERE b.id in (SELECT MAX(id) FROM table_b GROUP BY sid)