Is there a way to filter rows in a dynamic pivot stored procedure?

Question

I can filter columns but not rows.

Here is my iGuide Table data I use with my PIVOT:

---

/////////////////////////////////////////////////////

Zone    Enabled     Channel  DMA    Region    HQ       Machine
ACC         1        AEN    Norfolk  Other   virginia   dzsfk
ACC         1        CNN    Norfolk  Other   virginia   dzsfk
ACC         1        ESPN   Norfolk  Other   virginia   dzsfk
ACC         1        HIST   Norfolk  Other   virginia   dzsfk
ACC         1        FOOD   Norfolk  Other   virginia   dzsfk
ANJ         1        AEN    Paducah  Pacific hqs3ftbgwi adanj
ANJ         1        ESPN   Paducah  Pacific hqs3ftbgwi adanj
ANJ         1        HIST   Paducah  Pacific hqs3ftbgwi adanj
ANJ         1        CNN    Paducah  Pacific hqs3ftbgwi adanj
CHD         1        ESPN   Denver   Pacific hqs3ftbgwi adchd
CHD         1        FOOD   Denver   Pacific hqs3ftbgwi adchd
CHD         1        DISC   Denver   Pacific hqs3ftbgwi adchd
CHI         1        AEN    Denver   Pacific hqs3ftbgwi adchd
CHI         1        FOOD   Chico    Pacific hqs4ftbgwi adv1chicca
CHI         1        ESPN   Chico    Pacific hqs4ftbgwi adv1chicca
CHI         1        CNN    Chico    Pacific hqs4ftbgwi adv1chicca

/////////////////////////////////////////////////////

Here is an example of my initial result of Stored Procedure without any filters:

---

CHANNEL | ACC | ANJ | CHD | CHI |
AEN        1     1    NULL   1
CNN        1     1    NULL   1
ESPN       1     1     1     1  
FOOD       1    NULL   1     1
HIST       1     1    NULL  NULL
DISC     NULL   NULL   1    NULL
_________________________________________________

HERE is my current result I get after applying a zone @Filter = 'ACC':

_________________________________________________
CHANNEL | ACC |
AEN        1  
CNN        1
ESPN       1
FOOD       1
HIST       1
DISC      NULL
_________________________________________________

My desired result is to get this:

_________________________________________________
CHANNEL | ACC |
AEN        1  
CNN        1
ESPN       1
FOOD       1
HIST       1
_________________________________________________

How do I get rid of empty NULL rows when applying my filter?

HERE IS MY CODE:

    USE [Media_Ops]
    GO

    SET ANSI_NULLS ON
    GO
    SET QUOTED_IDENTIFIER ON
    GO
    ALTER Procedure [dbo].[Usp_GetWHERE]
    @Filter Varchar(MAX)

    AS

   DECLARE @columns NVARCHAR(MAX)      
           ,@sql NVARCHAR(MAX)

    SET @columns = N''
    --Get column names for entire pivoting
    SELECT @columns += N', ' + QUOTENAME(Zone)
      FROM (select distinct Zone 
            from iGuide  WHERE (DMA LIKE @Filter)   OR (Channel = @Filter) OR (@Filter = ' Select All') OR (@Filter = 'Select All') OR (Zone LIKE @Filter) OR (Machine LIKE @Filter) OR (Company LIKE @Filter) OR (HQ LIKE @Filter) OR (Region LIKE @Filter)
         ) AS T
    --select @columns
    SET @sql = N'
    SELECT  Distinct Channel, ' + STUFF(@columns, 1, 2, '') + '
    FROM iGuide 
    PIVOT
    (
      count(Zone) FOR Zone IN ('
      + STUFF(REPLACE(@columns, ', [', ',['), 1, 1, '')
      + ')
    ) AS Pivot1  ORDER BY Channel
    ' 
    PRINT @sql;
    EXEC sp_executesql @sql;

Answer 1

SQL DEMO Create a new variable @zone to filter before pivot

CREATE Procedure [dbo].[Usp_GetWHERE]
    @Filter Varchar(MAX)

AS

   DECLARE @columns NVARCHAR(MAX)      
           ,@sql NVARCHAR(MAX)
           ,@zone NVARCHAR(MAX)

    --Get column names for entire pivoting
    SET @columns = N''
    SELECT @columns += N', ' + QUOTENAME(Zone)
      FROM (select distinct Zone 
            from iGuide  WHERE (DMA LIKE @Filter)   OR (Channel = @Filter) OR (@Filter = ' Select All') OR (@Filter = 'Select All') OR (Zone LIKE @Filter) OR (Machine LIKE @Filter) OR (HQ LIKE @Filter) OR (Region LIKE @Filter)
         ) AS T

    --Get column names for filter source    
    SET @zone = N''
    SELECT @zone += N', ' + QUOTENAME(Zone, '''')
      FROM (select distinct Zone 
            from iGuide  WHERE (DMA LIKE @Filter)   OR (Channel = @Filter) OR (@Filter = ' Select All') OR (@Filter = 'Select All') OR (Zone LIKE @Filter) OR (Machine LIKE @Filter) OR (HQ LIKE @Filter) OR (Region LIKE @Filter)
         ) AS T

    SET @zone = '(' + substring(@zone, 3, len(@zone)-2) + ')';         

    SET @sql = N'
    SELECT  [Channel], ' + STUFF(@columns, 1, 2, '') + '
    FROM (SELECT Channel, [Zone]
          FROM iGuide 
          WHERE [Zone] IN ' + @zone + ')  as source
    PIVOT
    (
      count([Zone]) FOR [Zone] IN ('
      + STUFF(REPLACE(@columns, ', [', ',['), 1, 1, '')
      + ')
    ) AS Pivot1  ORDER BY Channel
    ' 
    select @sql;
    EXEC sp_executesql @sql;

GO 
EXECUTE [dbo].Usp_GetWHERE N'ACC';              

OUTPUT