SQL Server 2008 SELECT JOIN来自两个表

Question

I have two tables, the first one looks like this:

[Comparisons]

• Id (int)
• Car_Id1 (int)
• Car_Id2 (int)
• Slug (string)
• TimeStamp

The second one:

[VehicleSpecs]

• Id (int)
• Year (int)
• Make (string)
• Model (string)

I have this query

SELECT TOP 100 * 
FROM [Comparsions] 
WHERE 
ORDER BY [TimeStamp]

It returns the newest 100 records, but I need to replace the Car_Id1 and Car_Id2 with information from the second table like this: Car_Id1 -> [Year + Make + Model]

Answer 1

So what you'll need is two INNER JOIN s against the VehicleSpecs table, one for each Car_Id1 and Car_Id2 . I've aliased them as car1, car2 .

SELECT TOP 100
  c.Id,
  c.Slug,
  c.TimeStamp,
  /* Select the relevant columns from *both* of the joined tables */
  /* And give each column an alias to differentiate it from the other */
  car1.Year AS car1Year,
  car1.Make AS car1Make,
  car1.Model AS car1Model,
  car2.Year AS car2Year,
  car2.Make AS car2Make,
  car2.Model AS car2Model
FROM 
  Comparisons c
  /* Join first against VehicleSpecs for Car_Id1 */
  INNER JOIN VehicleSpecs car1 ON c.Car_Id1 = car1.Id
  /* Then once more for Car_Id2 */
  INNER JOIN VehicleSpecs car2 ON c.Car_Id2 = car2.Id
ORDER BY c.TimeStamp

You said you wanted the newest , so I assume you actually mean to use descending order on the timestamps:

ORDER BY c.TimeStamp DESC

Answer 2

Join against the second table twice:

select top 100
  c.Id, c.Slug, c.TimeStamp,
  s1.Year as Car1_Year, s1.Make as Car1_Make, s1.Model as Car1_Model,
  s2.Year as Car2_Year, s2.Make as Car2_Make, s2.Model as Car2_Model
from Comparsions c
inner join VehicleSpecs s1 on s1.Id = c.Car_Id1
inner join VehicleSpecs s2 on s2.Id = c.Car_Id2
order by c.TimeStamp desc

(Side note: You might want to correct the table name to Comparisons .)