首先必须保证所有字段都为字符串,各表以a1,b1,c1关联:
select
(select a1 from a where a.a1=b.b1 and a.a1=c.c1)||
(select b1 from b where a.a1=b.b1 and a.a1=c.c1)||
(select c1 from c where a.a1=b.b1 and a.a1=c.c1) field1,
select a2 from a where a.a1=b.b1 and a.a1=c.c1)||
(select b2 from b where a.a1=b.b1 and a.a1=c.c1)||
(select c2 from c where a.a1=b.b1 and a.a1=c.c1) field2,
select a3 from a where a.a1=b.b1 and a.a1=c.c1)||
(select b3 from b where a.a1=b.b1 and a.a1=c.c1)||
(select c3 from c where a.a1=b.b1 and a.a1=c.c1) field3
from a,b,c where a.a1=b.b1 and a.a1=c.c1 ;