I think is not linked with the blank parameter, it is related with the value in Column1.
When the column 1 is null, then the comparison with like is a little complex.
Can you please paste the error you are facing, or output when column1 is null?
When Column1 is NULL your calculation is: WHERE NULL LIKE NULL and this is NOT TRUE.
What do you want as result when one or both are NULLs?
For example I have 10records having column1 value as NULL.
Select * from table where column1 IS NULL -- It'l return 10 rows
In my above query, the parameter value may be 'AAA'/blank('').. If its value based on that it has to return rows..in my case no rows will return...If it's blank(''),it has to return 10 rows.....
If column1 is null, it didnt return any row
if "Parameter" is NULL or '' then return NULL rows else do the LIKE comparison?
WHERE (Parameter LIKE '%'|| TRIM(Column1) || '%')
OR (NULLIF(Parameter, '') IS NULL AND Column1 IS NULL)