Error : Invalid length parameter passed to the LEFT or SUBSTRING function

Question

My Function is as Following ::

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Create Function dbo.fnFcid(@url varchar)
 Returns int

 As

 BEGIN
 Return ( select ID from  TTI_fat.dbo.FormContext
          where caseId = (SELECT SUBSTRING(@url, PATINDEX('%&c=%', @url)+ 3, (PATINDEX('%&y=%', @url) - (PATINDEX('%&c=%', @url)+3)))) 
          and   YearID = (SELECT SUBSTRING(@url, PATINDEX('%&y=%', @url)+ 3, (PATINDEX('%&e=%', @url) - (PATINDEX('%&y=%', @url)+3)))) 
          and   EntityID = (SELECT SUBSTRING(@url, PATINDEX('%&e=%', @url)+ 3, (PATINDEX('%&g=%', @url) - (PATINDEX('%&e=%', @url)+3))))
          and   GroupID = (SELECT SUBSTRING(@url, PATINDEX('%&g=%', @url)+ 3, (PATINDEX('%&v=%', @url) - (PATINDEX('%&g=%', @url)+3)))) 
         )  
   END;
 Go

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when I am passing a following value to function

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select dbo.fnFcid('http://localh0st/web/forms/getForm.asp?page=FKYASDENPLFPg1V2014&c=9&y=283&e=1022&g=2&v=1&x=296807&j=161037&z=1')

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its shows me following error

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Msg 537, Level 16, State 2, Line 1
Invalid length parameter passed to the LEFT or SUBSTRING function.

Solution

Problem Fixed of my aboves question Its due to i forgot to mention varchar size while declaring function

Create Function dbo.fnFcid(@url varchar(max))