Many to many merge join on a unique lookup

CREATE UNIQUE CLUSTERED INDEX CntyCd ON #CntyCd(CntyCd)
 
CREATE UNIQUE NONCLUSTERED INDEX Edition ON #CntyCd(CntyCd,Edition)
 
ALTER TABLE [tCommon].[UnvPclID] ADD CONSTRAINT [tCommon_UnvPclID_PKC] PRIMARY KEY CLUSTERED ([CntyCD], [Edition], [PclId], [PclSeqNbr]) WITH (SORT_IN_TEMPDB = ON, FILLFACTOR  = 95) ON [Common]
GO
CREATE NONCLUSTERED INDEX [IDX_UnvPclID] ON [tCommon].[UnvPclID] ([UnvPclID]) INCLUDE ([CntyCD], [Edition], [PclId], [PclSeqNbr]) WITH (SORT_IN_TEMPDB = ON, FILLFACTOR  = 95) ON [Common]
GO
 
 
....
FROM    ( SELECT    up.CntyCd
                  , up.Edition
                  , up.PclId
                  , up.PclSeqNbr
                  , up.UnvPclID
          FROM      [tCommon].[UnvPclId] up
          WHERE     EXISTS (SELECT 1 FROM #CntyCd c WHERE up.CntyCd = c.CntyCd AND up.Edition = c.Edition)
        ) up
...