在给定日期的有效价格

Question

got a table with dates and prices.

Date                  Price
2012-01-01            25
2012-01-05            12
2012-01-10            10

Is there some kind of function that lets me find what the current price where at '2012-01-07'? Without me knowing of the other dates.

Pseudoquery: select price where currentprice('2012-01-07')

Thanks!

Answer 1

MySQL:

select price from your_table 
where date <= '2012-01-07'
order by date desc
limit 1

SQL Server:

select top 1 price from your_table 
where date <= '2012-01-07'
order by date desc

Answer 2

If you don't have use of ROW_NUMBER(), and want a generic solution, you need to join on a sub-query.

Get the date you want, then get the data for that date.

SELECT
  *
FROM
  yourTable
INNER JOIN
(
  SELECT MAX(yourDate) AS maxDate FROM yourTable WHERE yourDate <= @dateParameter
)
  AS lookup
    ON yourTable.yourDate = lookup.maxDate

Answer 3

 select price 
 from table1 t 
 where t.date = ( select max(t2.date) 
                  from table1 t2
                  where t2.date <= '2012-01-07' )

Note this is not the copy&paste answer, as we're not not knowing what is the datatype for your date column.