怎么根据查询结果执行不同的sql

[木杵]

如果表1存在id=1，执行：select * from 表1，否则执行：select * from 表2
Oracle要怎么写呢？
表1和表2结构一样，只是内容不一样

[卖水果的net]

-- 可以写成这样，但是建议你分两步写比较好。 select * from t1 where id = 1 union all select * from t2 where not exists(select * from t1 where id =1)

[lhdz_bj]

declare
v_cnt int;
begin
select count(1) into v_cnt from 表1 where id=1 and rownum<2;
if v_cnt>0 then
select * from 表1
else
select * from 表2
end if;
end;
大概这样吧，随手写的，没校对具体语法。

[wilson1966]

SELECT CASE WHEN rowcount > 0 THEN select * from 表1 ELSE SELECT * FROM 表2 END FROM ( SELECT count(*) rowcount FROM 表1 WHERE id=1 ) a

[YeHuai1991]

采用存储过程实现，支持3楼

[nayi_224]

select*from tab1 where exists(select*from tab1 t1 where t1.id = 1)
union all
select*from tab2 where not exists(select*from tab1 t2 where t2.id = 1)

[洪武哥]

select * from a1 where exists (select null from dual where a1.id=1) union all select * from a2 where not exists(select null from a1 where a1.id=1)