sorting - Sort string as number in sql server

Question

I have a column that contains data like this. dashes indicate multi copies of the same invoice and these have to be sorted in ascending order

790711
790109-1
790109-11
790109-2

i have to sort it in increasing order by this number but since this is a varchar field it sorts in alphabetical order like this

790109-1
790109-11
790109-2
790711

in order to fix this i tried replacing the -(dash) with empty and then casting it as a number and then sorting on that

select cast(replace(invoiceid,'-','') as decimal) as invoiceSort...............order by invoiceSort asc

while this is better and sorts like this

            invoiceSort
790711      (790711)   <-----this is wrong now as it should come later than 790109
790109-1    (7901091)
790109-2    (7901092)
790109-11   (79010911)

Someone suggested to me to split invoice id on the - (dash ) and order by on the 2 split parts

like=====> order by split1 asc,split2 asc (790109,1)

which would work i think but how would i split the column.

The various split functions on the internet are those that return a table while in this case i would be requiring a scalar function.

Are there any other approaches that can be used? The data is shown in grid view and grid view doesn't support sorting on 2 columns by default ( i can implement it though :) ) so if any simpler approaches are there i would be very nice.

EDIT : thanks for all the answers. While every answer is correct i have chosen the answer which allowed me to incorporate these columns in the GridView Sorting with minimum re factoring of the sql queries.

Answer 1

Judicious use of REVERSE, CHARINDEX, and SUBSTRING, can get us what we want. I have used hopefully-explanatory columns names in my code below to illustrate what's going on.

Set up sample data:

DECLARE @Invoice TABLE (
    InvoiceNumber nvarchar(10)
);

INSERT @Invoice VALUES
('790711')
,('790709-1')
,('790709-11')
,('790709-21')
,('790709-212')
,('790709-2')

SELECT * FROM @Invoice

Sample data:

InvoiceNumber
-------------
790711
790709-1
790709-11
790709-21
790709-212
790709-2

And here's the code. I have a nagging feeling the final expressions could be simplified.

SELECT 
    InvoiceNumber
    ,REVERSE(InvoiceNumber) 
        AS Reversed
    ,CHARINDEX('-',REVERSE(InvoiceNumber)) 
        AS HyphenIndexWithinReversed
    ,SUBSTRING(REVERSE(InvoiceNumber),1+CHARINDEX('-',REVERSE(InvoiceNumber)),LEN(InvoiceNumber)) 
        AS ReversedWithoutAffix
    ,SUBSTRING(InvoiceNumber,1+LEN(SUBSTRING(REVERSE(InvoiceNumber),1+CHARINDEX('-',REVERSE(InvoiceNumber)),LEN(InvoiceNumber))),LEN(InvoiceNumber)) 
        AS AffixIncludingHyphen
    ,SUBSTRING(InvoiceNumber,2+LEN(SUBSTRING(REVERSE(InvoiceNumber),1+CHARINDEX('-',REVERSE(InvoiceNumber)),LEN(InvoiceNumber))),LEN(InvoiceNumber)) 
        AS AffixExcludingHyphen
    ,CAST(
        SUBSTRING(InvoiceNumber,2+LEN(SUBSTRING(REVERSE(InvoiceNumber),1+CHARINDEX('-',REVERSE(InvoiceNumber)),LEN(InvoiceNumber))),LEN(InvoiceNumber))
        AS int)  
        AS AffixAsInt
    ,REVERSE(SUBSTRING(REVERSE(InvoiceNumber),1+CHARINDEX('-',REVERSE(InvoiceNumber)),LEN(InvoiceNumber))) 
        AS WithoutAffix
FROM @Invoice
ORDER BY
    -- WithoutAffix
    REVERSE(SUBSTRING(REVERSE(InvoiceNumber),1+CHARINDEX('-',REVERSE(InvoiceNumber)),LEN(InvoiceNumber))) 
    -- AffixAsInt
    ,CAST(
        SUBSTRING(InvoiceNumber,2+LEN(SUBSTRING(REVERSE(InvoiceNumber),1+CHARINDEX('-',REVERSE(InvoiceNumber)),LEN(InvoiceNumber))),LEN(InvoiceNumber))
        AS int)

Output:

InvoiceNumber Reversed   HyphenIndexWithinReversed ReversedWithoutAffix AffixIncludingHyphen AffixExcludingHyphen AffixAsInt  WithoutAffix
------------- ---------- ------------------------- -------------------- -------------------- -------------------- ----------- ------------
790709-1      1-907097   2                         907097               -1                   1                    1           790709
790709-2      2-907097   2                         907097               -2                   2                    2           790709
790709-11     11-907097  3                         907097               -11                  11                   11          790709
790709-21     12-907097  3                         907097               -21                  21                   21          790709
790709-212    212-907097 4                         907097               -212                 212                  212         790709
790711        117097     0                         117097                                                         0           790711

Note that all you actually need is the ORDER BY clause, the rest is just to show my working, which goes like this:

• Reverse the string, find the hyphen, get the substring after the hyphen, reverse that part: This is the number without any affix
• The length of (the number without any affix) tells us how many characters to drop from the start in order to get the affix including the hyphen. Drop an additional character to get just the numeric part, and convert this to int. Fortunately we get a break from SQL Server in that this conversion gives zero for an empty string.
• Finally, having got these two pieces, we simple ORDER BY (the number without any affix) and then by (the numeric value of the affix). This is the final order we seek.

The code would be more concise if SQL Server allowed us to say SUBSTRING(value, start) to get the string starting at that point, but it doesn't, so we have to say SUBSTRING(value, start, LEN(value)) a lot.