Example of a procedure using IF condition and it takes multiple training ID at any given time

Create Procedure Sp_test    
           
@ChannelID nvarchar(100),           
@DealerID nvarchar(100),           
@AreaID nvarchar(100),             
@ZoneID nvarchar(100),   
@TrainingID nvarchar(100)  ,
@sessionid nvarchar(100),         
@RoleID nvarchar(100)            
as           
           
declare  @str varchar(1000)           
Begin           
set @str= 'select distinct z1.Zone,A1.AreaName as AO ,D1.ID,D1.Code as dealerCode,D1.Name as DealerName,MPE1.ManPowerId,MP1.EmployeeCode,   
(MP1.FirstName + '''' + MP1.LastName) as Name,   
(select SkillName from dbo.Mas_Skills where ID=MPE1.SkillId) as empRole,MPT.TrainingId,MT.Code,MPT.TrainingCompletionDate   
 from DealerChannelMapping DM1,Dealer D1 ,Mas_Zone Z1,Mas_Area A1,   
  dbo.ManPowerExperience MPE1,   
 ManPower MP1 ,ManPowerTraining MPT,Mas_Training MT ,Mas_Skills MS 
where D1.ID=DM1.DealerID  and Z1.ID=A1.ZoneId  and MS.ID=MPE1.SkillId   
and MPE1.DealerID=D1.ID and MPT.TrainingId=MT.ID and  MS.IsActive=1  and MPE1.IsActive=1
and D1.IsActive=1 and MT.IsActive=1 and MPT.IsActive=1 and DM1.IsActive=1 and MP1.IsActive=1
and Z1.IsActive=1 and A1.IsActive=1 and
MPE1.ManpowerId=MP1.ID '           
           
if (@ChannelID <> 0)            
begin           
set @str= @str + ' and DM1.ChannelID='+@ChannelID            
end           
           
if (@DealerID <> 0)            
begin           
set @str= @str + ' and  DM1.DealerID='+@DealerID             
end           
           
           
if (@ZoneID <> 0)            
begin           
set @str= @str + ' and  Z1.ID='+@ZoneID             
end           
           
if (@AreaID <> 0)            
begin           
set @str= @str + ' and  A1.ID='+@AreaID            
end           
 if (@RoleID <> 0)            
begin           
set @str= @str + ' and  MPE1.SkillId='+@RoleID            
end            
 if (@TrainingID <> 0)            
begin           
set @str= @str + ' and MPT.TrainingId in (select TrainingId from DumyTrainingReadiness where sessionid = '''+@sessionid
    set @str= @str + ''')'       
end            
exec (@str)           
           
end