原来的语句是这样的：
　　select sum(sl0000) from xstfxps2 where
　　dhao00 in (
　　select dhao00 from xstfxps1 where trunc(ywrq00)=trunc(sysdate)
　　and khdm00='500000003913');
　　已用时间: 00: 02: 49.04
　　
　　Execution Plan
　　----------------------------------------------------------
　　0 SELECT STATEMENT Optimizer=CHOOSE
　　1 0 SORT (AGGREGATE)
　　2 1 NESTED LOOPS
　　3 2 TABLE ACCESS (FULL) OF 'XSTFXPS2'
　　4 2 TABLE ACCESS (BY INDEX ROWID) OF 'XSTFXPS1'
　　5 4 INDEX (UNIQUE SCAN) OF 'XSTFXPS1_PK' (UNIQUE)