一个有用的SQL语句

SELECT RelationID, Condition,
          (SELECT TOP 1 a.wfnodeid
         FROM wfnode a
         WHERE a.nodeid = b.nodeid) AS nodeid,
          (SELECT TOP 1 c.wfnodeid
         FROM wfnode c
         WHERE c.nodeid = b.childid) AS childid
FROM WFTmpNodeRelation b