想让结果集为：如果查询的结果为空则返回-1；非空则返回结果集；请各位达人路过帮帮忙！！！

[xabcxyz]

想让结果集为：如果select top 1 jc from db_log where cd = '0' order by id desc的结果为空则返回-1；非空则返回结果集
我试着写了两条语句都不行，请各位帮帮忙吧！！！！
select case when exists (select * from (select top 1 jc from db_log where cd = '0' order by id desc) C) then C.jc else -1 end as jc

select case when exists (select * from C) then C.jc else -1 end as jc from (select top 1 jc from db_log where cd = '0' order by id desc) C


谢谢！！！

[jminxuan]

declare @i int;

Set @i = -1;
Select top1 @i = jc from db_log where cd = '0' order by id desc

[让你望见影子的墙]

if exists( select * from (select top 1 jc from db_log where cd = '0' order by id desc) )
select * from (select top 1 jc from db_log where cd = '0' order by id desc)
else
return -1

[xabcxyz]

请教HEROWANG ：
两次执行(select top 1 jc from db_log where cd = '0' order by id desc) 不影响性能吗？

[zjcxc]

SELECT
	ISNULL(
			(select top 1 jc from db_log where cd = '0' order by id desc),
			-1)

[zoujp_xyz]

老大的语句好

[xabcxyz]

谢谢邹建！！

[BobHe]

3楼正解