Context Filter

In tableau  all the filters will compute independently.It means each and every   filter will access the complete data from the data source with out depending  on other filters.
If you want to create dependent filtering  in tableau then we have to make use of the context filters.In context filtering the context filter will act on the complete data source where as all the normal filters will acts on the data given by the context filters.

Advantages:           

                     
            1.  context filter will improve the performance.Reason being all the normal 
                  filters in context filtering will access only context filter but not the data
                  source.
            2.  context filter will   be appear in the grey color.
            3.  Always the context filters will appears on the top of the filter shelf. 
                  it is not possible  to change the position of the context filter.
            4.  While performing the context filtering tableau will create a temporary  
                 table to hold the context data.the data will be used by the normal filters                                 repeatedly.  tableau create that temporary table in the data source . 
            5.  If our data source is MS Excel,MS Access , Text file the temporary table
                   is  created as an MS Access in the tableau it self.
            6. If our data source are in the database like Oracle.SQL Server,DB2, etc
                 tableau  will create the temporary table in that database.
                 so to create the temporary table  on database we must have the 
                 permission to create the temporary table.
             7. For multi dimensional data sources tableau will not create any
                temporary  table.
             8.If  you want  to remove any context from the context filter right click 
              on the context  filter and select remove from the context. 
             9.If we removes the context from the context filter tableau will removes 
                 only the context but not filter from the filter shelf.simply it converts the 
                context  filter to the   normal filters.