select a.field1,a.field2 from
table1 a,table2 b
where a.customid=b.customid
and
(case when b.field3 is not null then a.field3=b.field3 else b.field3 is null end)
table1 a,table2 b
where a.customid=b.customid
and
(case when b.field3 is not null then a.field3=b.field3 else b.field3 is null end)
table1 a,table2 b
where a.customid=b.customid
and b.field3 is null
union
select a.field1,a.field2 from
table1 a,table2 b
where a.customid=b.customid and a.field3=b.field3
and b.field3 is not null
(case when b.field3 is not null then a.field3=b.field3 else b.field3 is null end)
的等于附近有错误