set explain on to aaa.txt命令产生的文件！

sc_px_jiangyun

set explain on to aaa.txt命令产生的文件如何阅读？
QUERY:
------
select * from lnsacctinfo a,lnscommass b where a.acctno=b.acctno and b.subsectio
n = 1 and a.loanstat !='06' and a.loanstat !='07' and a.loanstat !='08'

Estimated Cost: 110222
Estimated # of Rows Returned: 58387

  1) lntest.a: SEQUENTIAL SCAN

        Filters: ((lntest.a.loanstat != '06' AND lntest.a.loanstat != '08' ) AND
lntest.a.loanstat != '07' )

  2) lntest.b: INDEX PATH

    (1) Index Keys: acctno subsection   (Serial, fragments: ALL)
        Lower Index Filter: (lntest.a.acctno = lntest.b.acctno AND lntest.b.subs
ection = 1 )
NESTED LOOP JOIN
QUERY:
------
select * from lnsacctinfo a,lnscommass b where a.acctno=b.acctno and b.subsectio
n = 1 and a.loanstat !='06' and a.loanstat !='07' and a.loanstat !='08'

Estimated Cost: 110222
Estimated # of Rows Returned: 58387

  1) lntest.a: SEQUENTIAL SCAN

        Filters: ((lntest.a.loanstat != '06' AND lntest.a.loanstat != '08' ) AND
lntest.a.loanstat != '07' )

  2) lntest.b: INDEX PATH

    (1) Index Keys: acctno subsection   (Serial, fragments: ALL)
        Lower Index Filter: (lntest.a.acctno = lntest.b.acctno AND lntest.b.subs
ection = 1 )
NESTED LOOP JOIN

index path是啥意思？