请教一个语句的优化
哪位帮看看，给点建议

insert szy_ok
select distinct a.gdsid,a.gdsmc,a.xh,a.gys,fmid
from CITY b,szy_jg1 a  
where a.gdsid=b.gdsid AND a.gys=b.gys      
    and b.city =  '900'
    and b.fmid  in  ('0001','0002','0003') and b.flg1 <>'X'  
and not exists (select 1 from szy_ok c where c.gdsid = b.gdsid and c.gys = b.gys and c.rtptype = b.fmid)       
union 
select distinct a.gdsid,a.gdsmc,a.xh,a.gys,fmid
from LABEL b,szy_jg1 a  
where a.gdsid=b.gdsid AND a.gys=b.gys      
    and b.city =  '900'
    and b.fmid  in  ('0001','0002','0003') and b.flg1 <>'X'  
    and not exists (select 1 from szy_ok c where c.gdsid = b.gdsid and c.gys = b.gys and c.rtptype = b.fmid) 



--IO消耗
Table: CITY scan count 403720, logical reads: (regular=1697756 apf=0 total=1697756), physical reads: (regular=0 apf=0 total=0), apf IOs used=0
Table: szy_jg1 scan count 1, logical reads: (regular=27183 apf=0 total=27183), physical reads: (regular=0 apf=0 total=0), apf IOs used=0
Table: szy_ok scan count 149415, logical reads: (regular=23128183 apf=0 total=23128183), physical reads: (regular=0 apf=0 total=0), apf IOs used=0
Table: LABEL scan count 1, logical reads: (regular=279 apf=4 total=283), physical reads: (regular=0 apf=0 total=0), apf IOs used=0
Table: szy_jg1 scan count 5117, logical reads: (regular=15998 apf=0 total=15998), physical reads: (regular=0 apf=0 total=0), apf IOs used=0
Table: szy_ok scan count 5117, logical reads: (regular=793135 apf=0 total=793135), physical reads: (regular=0 apf=0 total=0), apf IOs used=0

SQL Server cpu time: 201200 ms.  SQL Server elapsed time: 207066 ms.


--表数据
sp_spaceused CITY     --4824054 
 
sp_spaceused szy_jg1  --403720
sp_spaceused szy_ok   --2379
sp_spaceused LABEL    --7232


--执行计划


QUERY PLAN FOR STATEMENT 1 (at line 2).


    STEP 1
        The type of query is INSERT.
        The update mode is direct.

        FROM TABLE
            szy_jg1
            a
        Nested iteration.
        Table Scan.
        Forward scan.
        Positioning at start of table.
        Using I/O Size 4 Kbytes for data pages.
        With LRU Buffer Replacement Strategy for data pages.

        FROM TABLE
            mkt.dbo.CITY
            b
        Nested iteration.
        Index : BA_GDSRTP_CITY
        Forward scan.
        Positioning by key.
        Keys are:
            city  ASC
            gys  ASC
            gdsid  ASC

        Run subquery 1 (at nesting level 1).
        Using I/O Size 4 Kbytes for index leaf pages.
        With LRU Buffer Replacement Strategy for index leaf pages.
        Using I/O Size 4 Kbytes for data pages.
        With LRU Buffer Replacement Strategy for data pages.
        TO TABLE 
 
            Worktable1.

    STEP 1
        The type of query is INSERT.
        The update mode is direct.

        FROM TABLE
            mkt.dbo.LABEL
            b
        Nested iteration.
        Table Scan.
        Forward scan.
        Positioning at start of table.

        Run subquery 1 (at nesting level 1).
        Using I/O Size 4 Kbytes for data pages.
        With LRU Buffer Replacement Strategy for data pages.

        FROM TABLE
            szy_jg1
            a
        Nested iteration.
        Index : szy_jg
        Forward scan.
        Positioning by key.
        Keys are:
            gys  ASC
            gdsid  ASC
        Using I/O Size 4 Kbytes for index leaf pages.
        With LRU Buffer Replacement Strategy for index leaf pages.
        Using I/O Size 4 Kbytes for data pages.
        With LRU Buffer Replacement Strategy for data pages.
        TO TABLE
            Worktable1.

    STEP 1
        The type of query is SELECT.
        This step involves sorting. 
 

        FROM TABLE
            Worktable1.
        Using GETSORTED
        Table Scan.
        Forward scan.
        Positioning at start of table.
        Using I/O Size 4 Kbytes for data pages.
        With MRU Buffer Replacement Strategy for data pages.
    STEP 1

NESTING LEVEL 1 SUBQUERIES FOR STATEMENT 1.

  QUERY PLAN FOR SUBQUERY 1 (at nesting level 1 and at line 7).

    Correlated Subquery.
    Subquery under an EXISTS predicate.


    STEP 1
        The type of query is SELECT.
        Evaluate Ungrouped ANY AGGREGATE.

        FROM TABLE
            szy_ok
            c
        EXISTS TABLE : nested iteration.
        Table Scan.
        Forward scan.
        Positioning at start of table.
        Using I/O Size 4 Kbytes for data pages.
        With LRU Buffer Replacement Strategy for data pages.

  END OF QUERY PLAN FOR SUBQUERY 1.

    STEP 2

NESTING LEVEL 1 SUBQUERIES FOR STATEMENT 1.

  QUERY PLAN FOR SUBQUERY 1 (at nesting level 1 and at line 14).

    Correlated Subquery.
    Subquery under an EXISTS predicate.


    STEP 1
        The type of query is SELECT.
        Evaluate Ungrouped ANY AGGREGATE. 
 

        FROM TABLE
            szy_ok
            c
        EXISTS TABLE : nested iteration.
        Table Scan.
        Forward scan.
        Positioning at start of table.
        Using I/O Size 4 Kbytes for data pages.
        With LRU Buffer Replacement Strategy for data pages.

  END OF QUERY PLAN FOR SUBQUERY 1.

[解决办法]
应该是执行计划吧。