oracle 存储过程cursor xxx is后面的select 语句能加判断条件得出吗？

Question

cursor XX is
select * from table;
能不能加条件判断？
如 cursor XX is
if (a=1) then
select * from table1;
elsif (a=2) then
select * from table2;
end if;

Answer 1

不能那样写，但是可以这样写
cursor xx is
SELECT case a when 1 then t1.field1, t1.field2, t1.field3...t1.fieldn
when 2 then t2.field1, t2.field2, t2.field3...t2.fieldn
ELSE NULL END
FROM table1 t1, table2 t2

Answer 2

如果是查询条件，可以用case when 构建，表的话好像没什么好办法。

有个办法，比较麻烦，
建一个临时表table3 like table1
if (a=1) then
insert into table3 select * from table1;
elsif (a=2) then
insert into table3 select * from table2;
end if;

cursor XX is
select * from table3