Select max int from varchar column

Question

I am trying to retrieve the largest number from a varchar column that includes both numbers and strings. An example of the data I\'m working with:

BoxNumber

Answer 1

Why not

SELECT MAX(CAST(Value AS Int)) FROM #bla 
WHERE ISNUMERIC(Value)=1 
    AND Value LIKE '%[0-9]%' 

then you're only dealing with numeric strings. In this case you may not need ISNUMERIC()

Answer 2

These answers are only half right. They succeed in isolating numeric values, but don't realize that when the underlying field is a number the Max function evaluates as characters (regardless of casting), reading left to right, so that 789 > 1000 because 7 > 1. A way around this might be to forget about casting and left pad the numbers with zeros to a common length, when Max in character mode should work.

Answer 3

Look into casting the column to an int, then selecting the MAX(). I don't know what it will do to columns that contain letters, but it's worth exploring.

http://doc.ddart.net/mssql/sql70/ca-co_1.htm

Answer 4

You should check this solution out for values like '+' and '-' as I think the IsNumeric function may return 1 for these values

Answer 5

You might try

Select MAX(BoxNumber) from {table} where IsNumeric(BoxNumber) = 1

Answer 6

The selected answer worked for me until I added this value to the temp table along with the others in the sample:

insert #bla values('1234')

I expected my max() result to now be 1234, but it remained at 789. Perhaps this is due to some collation setting, but I was able to reproduce on multiple databases. I found this query below worked for me, but I'd certainly be interested to hear if there is a more efficient way of doing this. Also, I did not want to include any decimal values, so I excluded anything with a period as well.

SELECT MAX(CAST(Value AS Int)) FROM #bla 
WHERE ISNUMERIC(Value)=1 
    AND Value NOT LIKE '%[a-z]%' 
    AND Value NOT LIKE '%.%'