Question

I am having problems finding a solution for what I thought would be straight forward. Here is an example of what I am trying to do.

TABLE A  
time  |  state  
10:00 |   up  
10:09 |  down  
10:12 |   up  

TABLE B  
time  |  data  
10:05 |  abc  
10:07 |  def  
10:11 |  ghi  

I would like to join tables A and B maintaining all data in B, something like

SELECT tableB.time, tableB.data, tableA.status  
INTO my_results  
FROM tableB  
LEFT JOIN tableA  
WHERE tableB.time > (MAX(tableA.time) < tableB.time)  

So the my_results table would look like the following:

TABLE my_results  
time  |  data  | state  
10:05 |  abc   |  up  
10:07 |  def   |  up  
10:11 |  ghi   | down  

Table A Structure

source, varchar
destination, varchar
time, datetime
status, varchar

Table B Structure
tstamp, datetime
source, varchar
destination, varchar

This is the relevant information. Hopefully this is helpful.

Answer 1

Here’s a solution for SQL Server:

select  b.time
,       b.data
,       a.state
from    B
outer apply
        (
        select  top 1 *
        from    A
        where   A.time < B.time
        order by
                A.time desc
        ) as A

Live example at SQL Fiddle.