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
123
A5
789
B1

I need to return the largest number (789 in this case) from the column while ignoring the non-numeric values of A5 and B1.

I have found solutions that use custom functions to solve the problem, but I need something that can be executed ad-hoc query without relying on custom functions or procs.

Answer 1

you need a combination because of the fact that isnumeric returns 1 for the following things

select isnumeric('+'),isnumeric('5d2') 

your where clause would be like this

WHERE VALUE NOT LIKE '%[a-z]%'
        AND ISNUMERIC(VALUE) = 1

create table #bla (value varchar(50))
insert #bla values('123')
insert #bla values('a5')
insert #bla values('789')
insert #bla values('b1')

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

I wrote about this here ISNUMERIC Trouble

Answer 2

You might try

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

Answer 3

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()