title: Error when passing null parameter
body: <p>If the created date time is empty or no value in it i want to return whole table. If it contain date I want to return table data greater that that date. here below I submit a code but it gives data when there is a parameter but it show a error like this Procedure <code>SelectRotarian_AllByCreatedDatetime</code> 
  Procedure or function <code>SelectRotarian_AllByCreatedDatetime</code> expects parameter <code>@createdDateTime</code>, which was not supplied.</p>
  
  <p>(1 row(s) affected)</p>
  
  <pre><code>ALTER PROCEDURE [dbo].[SelectRotarian_AllByCreatedDatetime]
      @createdDateTime varchar(50)
  AS
  BEGIN
  
      SET NOCOUNT ON;
  
      if (Coalesce(@createdDateTime,'') = '')
      begin
             select [id]
        ,[surName]
        ,[firstName]
        ,[secondName]
        , [address]
        , [gender]
        ,[picture]
        ,[email]
        ,[phoneNumber]
        ,[DOB]
        ,[vocation]
        ,[bloodGroup_id]
        ,[club_id]
        ,[createdDateTime]
      FROM [rotary_rotarian]
       end 
       else 
       begin
  
             SELECT[id]
        ,[surName]
        ,[firstName]
        ,[secondName]
        , [address]
        , [gender]
        ,[picture]
        ,[email]
        ,[phoneNumber]
        ,[DOB]
        ,[vocation]
        ,[bloodGroup_id]
        ,[club_id]
        ,[createdDateTime]
      FROM [rotary_rotarian]
      where [createdDateTime] &gt; CAST(@createdDateTime AS DateTime)
        end
       END
  </code></pre>
  
  <p>so please help me</p>