set @y :=  if ( (select count(k_prisf) from prisf where k_spisf= 139  and k_organ = 316 )> 0 , 
( select k_prisf from prisf where k_organ= 316  
and znf=(select min(znf) from prisf where k_organ= 316  and zdel= 0  and znf!= 0 )),  
( select k_prisf from prisf where k_organ= 316  
and znf=(select min(znf) from prisf where k_organ= 316  and zdel= 0 ))); 

select if (prisf.k_spisf = 139 ,prisf.k_prisf,nfs.k_nfs) as id ,

if (  prisf.k_spisf = 139 ,  prisf.znf, nfs.znfs)  as znf  
from prisf , nfs,spisf 
where  prisf.k_spisf=nfs.k_spisf 
and prisf.k_spisf=spisf.k_spisf 
and nfs.zdel= 0  
and prisf.k_prisf=@y ;