How to get least value from table in sql

Question

I am getting the top value and least value from table,table accepting the nulls also.i am able to get the top value but not the low value.

This is my table data:

PostBidId UserId   PostId        BidAmount
-------------------------------------------------
1691       159       1239   
1684       147       1239        100000000000000
1683       147       1239        12345666666
1680       147       1239        6777777
1682       147       1239        900
1681       147       1239        90000000

My top value is 100000000000000 , low value id 900 .

This is my code:

SELECT TOP(1) 
    BidAmount AS HighestBid, '0' AS LowestBid 
FROM 
    [dbo].[Bids] 
WHERE
    PostId = 1239 AND BidAmount != '' 
ORDER BY
    BidAmount ASC

Output is: 100000000000000

SELECT
    MIN (BidAmount) AS LowestBid, '0' AS HighestBid 
FROM 
    [dbo].[Bids] 
WHERE
    PostId = 1239 AND BidAmount != '' 

Output is: 100000000000000 , what I am expecting is: 900 .

Answer 1

    SELECT MIN (CAST (BidAmount as bigint)) AS LowestBid, '0' AS HighestBid
    FROM [dbo].[Bids] 
    WHERE PostId = 1239 AND BidAmount != ''