SQL查询SSRS中的数据集

Question

I put two parameters in a query; [A_from] and [A_to] to decide some value in table for data set.

The both of parameters allow Null/empty and the value changes by parameter as you can see below. How can I write query for this? (Tried case statement, but doesn't work..)

Input)                 Output)
A_From and A_To        some Value Between A_From And A_To 
Only A_From            some value >= A_From
Only A_To              some value <= A_To
Both NULL              * (all) 

Answer 1

Since comparisons to null always yield false , you can use this:

select *
from my_table t
where
  (t.value >= A_From and t.value <= A_To) or
  (t.value >= A_From and A_To is null) or
  (A_From is null and t.value <= A_To) or
  (A_From is null and A_to is null)