查询返回 SQL 中列的第一个结果？

Question

In SQL, is there a simple way to return all the rows containing the top instance of a value in a column?

Given the table below...

Size    Color    Price
S       Red      1
S       Green    4
S       Blue     7
M       Olive    45
M       Black    99
M       Orange   153
L       Purple   4
L       Red      75
L       Blue     98

I want to return...

Size    Color    Price
S       Red      1
M       Olive    45
L       Purple   4

Answer 1

You can try a CTE function, and ROW_NUMBER() , to accomplish this:

This accomplishes it as descending which you say in the comments

;WITH CTE AS(
    SELECT myTable.*
    , RN = ROW_NUMBER()OVER(PARTITION BY Size ORDER BY Price DESC)
    FROM myTable 
)
SELECT Size, Color, Price FROM CTE
WHERE RN = 1

This accomplishes your desired results:

;WITH CTE AS(
    SELECT myTable.*
    , RN = ROW_NUMBER()OVER(PARTITION BY Size ORDER BY Price ASC)
    FROM myTable 
)
SELECT Size, Color, Price FROM CTE
WHERE RN = 1
ORDER BY
  CASE Size
    WHEN 'S' THEN 1
    WHEN 'M' THEN 2
    WHEN 'L' THEN 3
  END

An example SQL FIDDLE is here so you can see a demo.

Influenced from: Select the first instance of a record

Answer 2

You require to partition your data to get rownums assigned to each partitioned size and then whichever is the first partition thats gonna be the result as below

     Select size, color, price from
         (Select Size, Color,Price, 
         row_number() 
        over (partition by size order by 
             Price) as rn
       from mytable) t where t.rn =1