SQL> create view c as
2 select nvl(a.n1,b.n1),nvl(a.n2,b.n2),n3,n4 from a full join b
3 on a.n1=b.n1 and a.n2=b.n2;
select nvl(a.n1,b.n1),nvl(a.n2,b.n2),n3,n4 from a full join b
*
ERROR at line 2:
ORA-00998: must name this expression with a column alias
2 select nvl(a.n1,b.n1),nvl(a.n2,b.n2),n3,n4 from a full join b
3 on a.n1=b.n1 and a.n2=b.n2;
select nvl(a.n1,b.n1),nvl(a.n2,b.n2),n3,n4 from a full join b
*
ERROR at line 2:
ORA-00998: must name this expression with a column alias
select nvl(a.n1,b.n1) n1,nvl(a.n2,b.n2) n2,n3,n4 from a full join b
on a.n1=b.n1 and a.n2=b.n2; 为表达式赋予一个别名。
这个错误说得已经很明确了,遇到有明显示提示,研究一下错误提示,你会进步得更快哈