如何在Oracle中重复查询

Question

I need to repeat this query 100 times. I think I should use loop function but didn't find any solutions on how to do it.

select case when DBMS_RANDOM.value >= 0 and DBMS_RANDOM.value<=0.053 then 1
            when DBMS_RANDOM.value > 0.053 and DBMS_RANDOM.value <= 0.097 then 2
            when DBMS_RANDOM.value > 0.097 and DBMS_RANDOM.value <= 0.142 then 3
end random_groups
from temp_trt;

here is the sample data of temp_trt enter image description here

Answer 1

Each call of DBMS_RANDOM.value() returns a different value . Consequently there is no guarantee that any call will fall between any of your bounds. In fact it's statistically unlikely. Consequently most of the time you'll get a NULL returned, because you have defined no ELSE branch.

Here is an alternate solution which generates one hundred random values.

with dr as (
    select DBMS_RANDOM.value val
    from dual
    connect by level <= 100 
)
select dr.val
      , case when dr.val >= 0 and dr.val<=0.053 then 1
            when dr.val > 0.053 and dr.val <= 0.097 then 2
            when dr.val > 0.097 and dr.val <= 0.142 then 3
            else 4 
end random_groups
from dr
;

Given the way your code defines the bounds of the branches, most of the random_groups will be 4 .

---

It's not clear from your posted (toy?) code what the role of TEMP_TRT is, so I decided to ignore it. Please edit your question to add more detail if this makes you unhappy

Answer 2

You can use row generation tecnique by select level ... connect by level >= 100 structure as

select level, rg.random_groups
 from
    ( select case when DBMS_RANDOM.value >= 0 and DBMS_RANDOM.value<=0.053 then 1
                when DBMS_RANDOM.value > 0.053 and DBMS_RANDOM.value <= 0.097 then 2
                when DBMS_RANDOM.value > 0.097 and DBMS_RANDOM.value <= 0.142 then 3
     end random_groups
    from dual ) rg
connect by level <= 100