How do I sort a VARCHAR column in SQL server that contains numbers?

I have a VARCHAR column in a SQL Server 2000 database that can contain either letters or numbers. It depends on how the application is configured on the front-end for the customer.

When it does contain numbers, I want it to be sorted numerically, e.g. as "1", "2", "10" instead of "1", "10", "2". Fields containing just letters, or letters and numbers (such as 'A1') can be sorted alphabetically as normal. For example, this would be an acceptable sort order.

1
2
10
A
B
B1

What is the best way to achieve this?

Solution 1:

One possible solution is to pad the numeric values with a character in front so that all are of the same string length.

Here is an example using that approach:

select MyColumn
from MyTable
order by 
    case IsNumeric(MyColumn) 
        when 1 then Replicate('0', 100 - Len(MyColumn)) + MyColumn
        else MyColumn
    end

The 100 should be replaced with the actual length of that column.

Solution 2:

There are a few possible ways to do this.

One would be

SELECT
 ...
ORDER BY
  CASE 
    WHEN ISNUMERIC(value) = 1 THEN CONVERT(INT, value) 
    ELSE 9999999 -- or something huge
  END,
  value

the first part of the ORDER BY converts everything to an int (with a huge value for non-numerics, to sort last) then the last part takes care of alphabetics.

Note that the performance of this query is probably at least moderately ghastly on large amounts of data.

Solution 3:

select
  Field1, Field2...
from
  Table1
order by
  isnumeric(Field1) desc,
  case when isnumeric(Field1) = 1 then cast(Field1 as int) else null end,
  Field1

This will return values in the order you gave in your question.

Performance won't be too great with all that casting going on, so another approach is to add another column to the table in which you store an integer copy of the data and then sort by that first and then the column in question. This will obviously require some changes to the logic that inserts or updates data in the table, to populate both columns. Either that, or put a trigger on the table to populate the second column whenever data is inserted or updated.

Solution 4:

SELECT *, CONVERT(int, your_column) AS your_column_int
FROM your_table
ORDER BY your_column_int

OR

SELECT *, CAST(your_column AS int) AS your_column_int
FROM your_table
ORDER BY your_column_int

Both are fairly portable I think.

Solution 5:

you can always convert your varchar-column to bigint as integer might be too short...

select cast([yourvarchar] as BIGINT)

but you should always care for alpha characters

where ISNUMERIC([yourvarchar] +'e0') = 1

the +'e0' comes from http://blogs.lessthandot.com/index.php/DataMgmt/DataDesign/isnumeric-isint-isnumber

this would lead to your statement

SELECT
  *
FROM
  Table
ORDER BY
   ISNUMERIC([yourvarchar] +'e0') DESC
 , LEN([yourvarchar]) ASC

the first sorting column will put numeric on top. the second sorts by length, so 10 will preceed 0001 (which is stupid?!)

this leads to the second version:

SELECT
      *
    FROM
      Table
    ORDER BY
       ISNUMERIC([yourvarchar] +'e0') DESC
     , RIGHT('00000000000000000000'+[yourvarchar], 20) ASC

the second column now gets right padded with '0', so natural sorting puts integers with leading zeros (0,01,10,0100...) in correct order (correct!) - but all alphas would be enhanced with '0'-chars (performance)

so third version:

 SELECT
          *
        FROM
          Table
        ORDER BY
           ISNUMERIC([yourvarchar] +'e0') DESC
         , CASE WHEN ISNUMERIC([yourvarchar] +'e0') = 1
                THEN RIGHT('00000000000000000000' + [yourvarchar], 20) ASC
                ELSE LTRIM(RTRIM([yourvarchar]))
           END ASC

now numbers first get padded with '0'-chars (of course, the length 20 could be enhanced) - which sorts numbers right - and alphas only get trimmed