Question

I have a string in my stored proc like ',,,sam,,bob,' or ',,,'
from the above string I have to delete multiple commas from it, it must look like
'sam,bob,' or only if ',,,' then '' .
I must use only Sql Server Functions.
Im using Sql Server 2008 and .Net 3.5

Thanks in advance.

Answer 1

This works for strings that are exclusively commas or have up to 398 contiguous commas.

 SELECT 
     CASE 
         WHEN TargetString NOT LIKE '%[^,]%' 
             THEN '' /*The string is exclusively commas*/
         ELSE 
            REPLACE(REPLACE(REPLACE(REPLACE(REPLACE(TargetString,
            REPLICATE(',',16),','), /*399/16 = 24 remainder 15*/
            REPLICATE(',',8),','),  /* 39/ 8 =  4 remainder 7*/
            REPLICATE(',',4),','),  /* 11/ 4 =  2 remainder 3*/
            REPLICATE(',',2),','),  /*  5/ 2 =  2 remainder 1*/
            REPLICATE(',',2),',')   /*  3/ 2 =  1 remainder 1*/
         END
 FROM T    

Add extra powers of 2 at the top if you need more or remove from the top if you need less. The comments by each stage indicate the smallest number that this stage will not deal with successfully.

All the comment lines are in this format

/*  L/D    =  Q remainder R */

D:    Corresponds to the length of the string generated by `REPLICATE`
R:    Is always D-1
Q+R:  Form L for the next step

So to extend the series upwards with another REPLICATE(',',32),',') stage

D = 32 
R = 31
Q = 368 (399-31)
L = (368 * 32) + 31 = 11807

So that would deal with sections of commas up to 11,806 characters.