MySQL查找并合并最接近日期范围的记录

Question

Been at this an embarrassing number of hours and have read similar posts here but not finding one that answer this question.

Have a table similar to this [ID is PK/Auto, Date is date field]

ID, Date, Vehicle, Odometer
1, 1/7/14, A16, 55512
2, 1/9/14, A16, 55600
3, 1/10/14, A16, 55600
4, 1/29/14, A16, 56213
5, 1/4/14, A17, 99512
6, 1/12/14, A17, 99600
7, 1/16/14, A17, 99600
8, 1/22/14, A17, 99213

I want to create a query (ultimately will be a stored proc) where I pass in TWO date parameters, "from" and "to", and it returns a list grouped by vehicle like this (example using 1/1/14 and 1/31/14 as date parameters):

Vehicle, From_ID, From_Date, From_Odometer, To_ID, To_Date, To_Odometer
A16, 1, 1/7/14, 55512,  4, 1/29/14, 56213
A17, 5, 1/4/14, 99512, 8, 1/22/14, 99213

Have tried multiple combinations of queries, subqueries, views with DATEDIFF and MAX combined with Date <= but not getting data lined up how I need it.

For example:

select 
table.ID
, max(table.`Date`) as TheDate
, table.Odometer
FROM table
where table.Odometer > 0 
and table.`Date`<= str_to_date('2/1/14','%m/%d/%Y');

Is an attempt to get PART of what I need but yields the correct date but incorrect ID and incorrect Odometer.

Any suggestions?

Answer 1

Assuming that Date is in fact a date type, and that ID is an autoincrementing primary key and the data is being entered in the date the odometer inspections took place (and therefore you can infer that the earlier the ID, the earlier the date and odometer reading), then this should work :

SELECT
    from_to.Vehicle,
    from_table.ID       AS From_ID,
    from_table.Date     AS From_Date,
    from_table.Odometer AS From_Odometer,
    to_table.ID         AS To_ID,
    to_table.Date       AS To_Date,
    to_table.Odometer   AS To_Odometer
FROM (
    SELECT
        vehicle,
        MIN(ID) AS From_ID,
        MAX(ID) AS To_ID
    FROM
        `table`
    WHERE
        Date BETWEEN '2014-01-01' AND '2014-01-31'
    GROUP BY 1
) from_to
INNER JOIN `table` from_table
    ON from_table.ID = from_to.From_ID
INNER JOIN `table` to_table
    ON to_table.ID = from_to.To_ID

If you can't assumed that the ID represents records in ascending date order, then you could extract the MIN and MAX values of Odometer and use that to join to the from_table and to_table. Note that you will run into trouble that way if you ever have two records for the same vehicle with the same odometer readings. The SQL to cope with that would be larger; instead of joining to table for you from_table and to_table, you would be joining to a subquery guaranteed to return one record per vehicle.