Match on longest string match

Question

I running an UPDATE statement, based on a JOIN from another table to identify and add the correct 'Destination' code

Below is my code.

UPDATE [BILLING] 
SET    [BILLING].[BILLDESTINATION] = [Orbisrates].[dbo].[RATES].[DESTINATION] 
FROM   [OrbisRates].[dbo].[RATES] 
       INNER JOIN [OrbisBilling].[dbo].[BILLING] 
               ON [OrbisBilling].[dbo].[BILLING].[TO] LIKE 
                  [RATES].[DESTINATION] + ''%'' 

I largely works much the matching is not correct.

Here are the example codes in my destination list

1
100
1001

The trouble is that telephone number 1001999 returns 100 as the Destination, where as I need it to match the longest correct match, so I want it to return 1001.

What would be the correct syntax to match the longest/best match?

Any help greatly appreciated.

EDIT - FULL CODE HERE

DECLARE @tablevalue NVARCHAR(MAX), @sql NVARCHAR(MAX); 

DECLARE table_value_cursor CURSOR FOR
    SELECT DISTINCT [Tariff Lookup] 
    FROM [OrbisBilling].[dbo].[masked_2014-06-30-2014-06-01-customer325]; OPEN table_value_cursor  
    FETCH NEXT FROM table_value_cursor INTO @tablevalue WHILE @@FETCH_STATUS = 0  
    BEGIN SELECT @sql = N'

        UPDATE [masked_2014-06-30-2014-06-01-customer325] 
        SET [masked_2014-06-30-2014-06-01-customer325].[Sell Price] = 
        (CASE WHEN (DATEPART(hh,[OrbisBilling].[dbo].[masked_2014-06-30-2014-06-01-customer325].[ConnectTime]) >= 8 AND DATEPART(hh,[OrbisBilling].[dbo].[masked_2014-06-30-2014-06-01-customer325].[ConnectTime]) <= 17)
        THEN ROUND ([Orbisrates].[dbo].[Orbis_Import_June2014].[Peakperminute]/60*[OrbisBilling].[dbo].[masked_2014-06-30-2014-06-01-customer325].[ChargedTimeSecs]+[Orbisrates].[dbo].[Orbis_Import_June2014].[Peakconnect],4)
        ELSE ROUND ([Orbisrates].[dbo].[Orbis_Import_June2014].[OffPeakperminute]/60*[OrbisBilling].[dbo].[masked_2014-06-30-2014-06-01-customer325].[ChargedTimeSecs]+[Orbisrates].[dbo].[Orbis_Import_June2014].[OffPeakconnect],4)
        END)
        FROM [OrbisRates].[dbo].'+ @tablevalue +'
        INNER JOIN [OrbisBilling].[dbo].[masked_2014-06-30-2014-06-01-customer325] on [OrbisBilling].[dbo].[masked_2014-06-30-2014-06-01-customer325].[To] LIKE '+ @tablevalue +'.[Destination]+ ''%''
        WHERE [OrbisBilling].[dbo].[masked_2014-06-30-2014-06-01-customer325].[tariff lookup] = '''+ @tablevalue +'''';

EXEC sp_executesql @sql; 
FETCH NEXT FROM table_value_cursor 
INTO @tablevalue; 
END CLOSE table_value_cursor 
DEALLOCATE table_value_cursor;

Answer 1

Here is your query rewritten with aliases so it is easier to read (at least for me):

UPDATE b
SET BillDestination = r.Destination
FROM OrbisRates.dbo.Rates r INNER JOIN
     OrbisBilling.dbo.Billing b
     on b.[To] LIKE r.Destination + '%';

The problem that you have is multiple matches. One way to solve this is with a subquery:

UPDATE b
    SET BillDestination = (SELECT TOP 1 r.Destination
                           FROM OrbisRates.dbo.Rates r
                           WHERE b.[To] LIKE r.Destination + '%'
                           ORDER BY LEN(r.Destination) DESC
                          ) 
    FROM OrbisBilling.dbo.Billing b;