1. 第一张表加并发

select /*+ PARALLEL(t1, 5) */count(*) 
from table1 t1, table2 t2 
where t1.pk = t2.pk 

2. 两张表都加并发

select /*+ PARALLEL(t1, 5)  PARALLEL(t2, 5) */count(*) 
from table1 t1, table2 t2 
where t1.pk = t2.pk