SQL查询S3D模型中的变等级连接

最近有人问SQL查询出变等级的连接。经测试，示例如下：

select distinct t1.con1oid as conoid,

t1.part1name ,t1.part1oid,

t1.spec1name,t2.part2name,t2.spec2name,t2.part2oid from (select xx.oid as con1oid,

xasd.oid as part1oid, ni.ItemName as part1name,sd.SpecName as spec1name from JRteDistribConnection xx

join

 XRelConnectionAndPartOcc zx on zx.oidorigin = xx.oid

join JRtePathGenPart xasd on xasd.Oid = zx.OidDestination

join JNamedItem ni on ni.Oid = xasd.Oid

join YPartsToRunSpecification ss on ss.OidDestination = xasd.oid

join JDPipeSpec sd on sd.oid = ss.OidOrigin) t1

join (

select xx.oid as con2oid,

xasd.oid as part2oid, ni.ItemName as part2name,sd.SpecName as spec2name from JRteDistribConnection xx

join

 XRelConnectionAndPartOcc zx on zx.oidorigin = xx.oid

join JRtePathGenPart xasd on xasd.Oid = zx.OidDestination

join JNamedItem ni on ni.Oid = xasd.Oid

join YPartsToRunSpecification ss on ss.OidDestination = xasd.oid

join JDPipeSpec sd on sd.oid = ss.OidOrigin) t2 on t1.con1oid = t2.con2oid

where t1.part1oid <> t2.part2oid and t1.spec1name <> t2.spec2name