SELECT a1.xm,a1.a1,a2.a2 FROM a1,a2 WHERE a2.xm=a1.xm UNION select a1.xm,a1.a1,0 FROM a1 WHERE a1.xm NOT in (SELECT a2.xm FROM a2) UNION select a2.xm,0,a2.a2 FROM a2 WHERE a2.xm NOT in (SELECT a1.xm FROM a1)
[此贴子已经被作者于2023-4-9 23:22编辑过]