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For each value in one table, select nearest value in another table

For each value in one table, select nearest value in another table

For each value in one table, select nearest value in another table

This is pretty simple to describe:
Table A & B both have a date field. I need a query/procedure which will do:
SELECT A.date, { max(B.date) where B.date < A.date}


A.date.... B.date
======.... ======
10/10/2006 01/01/1999
01/04/2007 12/12/2006

Result: A.date | Max B.date < A.date
10/10/2006 01/01/1999 // the biggest date in B which is < than 10/10/2006
01/04/2007 12/12/2006
So each row contains the date of an A, and the biggest date in B which is less than this value. It seems like it should be so simple but I just can't get it to work in a query, and I don't know the syntax Sybase use for writing procedures - if I were in Oracle I'd have given up and written a FOR loop by now... but a query would be neater anyway.

Many thanks for any help.

RE: For each value in one table, select nearest value in another table


your question lacks a little information. Do you have any other join conditions between tables A and B?
What RDBMS are you using (Oracle, DB2, SQLserver, etc)?

But let's give it a try (this is based on Oracle):
select a.date
     , max(case
           when a.date > b.date then b.date
           else null
from table1 a
   , table2 b
where join_condition
group by a.date

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