So part of my query is like this

select 
   column_a,
   0.75 * power(0.93, (0.1428 * column_b))

let's say column_b has the value of 3 is there a way to represent this line 0.75 * power(0.93, (0.1428 * column_b)) as this?

0.75 * power(0.93, (0.1428 * 3))   0.75 * power(0.93, (0.1428 * 2))   0.75 * power(0.93, (0.1428 * 1))

Basically, for what ever value column_b has, the function repeats. Is there a way to represent this in Postgres sql?

CodePudding user response：

Since this calculation will find the sum of 0.75 * power(0.93, (0.1428 * column_b)) repeated by the number of times in column_b, you could use generate_series to genera the increments to the amount in column_b before summing the result of this calculation eg.

Schema (PostgreSQL v13)

create table sample (
   column_a char(1),
   column_b int
);

insert into sample values ('a',3), ('b',2);

Using generate_series to generate the possible numbers

select 
    column_a,
    column_b,
    array(
        select b_val
        from generate_series(1,column_b) b_val
    ) as computed_column
from sample;

Finding the sum of the repeated calculation

select 
    column_a,
    column_b,
    (
        select sum(0.75 * power(0.93, (0.1428 * b_val)))
        from generate_series(1,column_b) b_val
    ) as computed_column
from sample;

View working demo on DB Fiddle