left outer join 问题

Question

select Salesinvoices.SalesInvoiceID,SalesInvoiceItems.SalesInvoiceItemID,Salesinvoices.Companyid,Salesinvoices.Departmentid,Salesinvoices.Payer,Salesinvoices.Billdate,SalesinvoiceItems.Materialid,Salesinvoices.Employeeid,SaleQuantity,TaxInPrice,TaxInValue,TaxControlCode,
       0,0,0,0,Arapclearitems.*
from SalesInvoiceItems
     inner join SalesInvoices on SalesInvoices.Salesinvoiceid=SalesInvoiceItems.Salesinvoiceid
     left outer join ARAPClearItems
             inner join ARAPClears on ARAPClears.Clearid =ARAPClearItems.Clearid  
      on nvl(ARAPClearItems.ARAPbillID,' ') =SalesInvoiceItems.Salesinvoiceid and nvl(ARAPClearItems.BillItemID,' ')=SalesInvoiceItems.SalesinvoiceItemID and nvl(ARAPClearitems.Invsign,' ') = '1'
     where companyid='010101' and substring(billdate,1,6)='200703' and payer='00001964'
为什么与
select Salesinvoices.SalesInvoiceID,SalesInvoiceItems.SalesInvoiceItemID,Salesinvoices.Companyid,Salesinvoices.Departmentid,Salesinvoices.Payer,Salesinvoices.Billdate,SalesinvoiceItems.Materialid,Salesinvoices.Employeeid,SaleQuantity,TaxInPrice,TaxInValue,TaxControlCode,
       0,0,0,0,Arapclearitems.*
from SalesInvoiceItems
     inner join SalesInvoices on SalesInvoices.Salesinvoiceid=SalesInvoiceItems.Salesinvoiceid
     left outer join ARAPClearItems
             
      on nvl(ARAPClearItems.ARAPbillID,' ') =SalesInvoiceItems.Salesinvoiceid and nvl(ARAPClearItems.BillItemID,' ')=SalesInvoiceItems.SalesinvoiceItemID and nvl(ARAPClearitems.Invsign,' ') = '1'
     where companyid='010101' and substring(billdate,1,6)='200703' and payer='00001964'
执行结果不一样？下面的可以出来六条纪录。但是上面的没有纪录？就是因为left outer join没有匹配上吗？但是left outer join 不应该影响纪录的条数吧~

Answer 1

上面的语句有问题:
      inner join ARAPClears ON ARAPClears.Clearid =ARAPClearItems.Clearid     ONnvl(ARAPClearItems.ARAPbillID,' ') =SalesInvoiceItems.Salesinvoiceid and nvl怎么又出来个on?

Answer 2

好好看看内、外，左、右关联的区别吧.再看看SQL语句的优化问题.