How can I create a column in postgres from values and selections based on other columns?

Question

I want to create a new field (or two) in my table that is a concatenation of other fields, which seems relatively straightforward. But what is the case syntax or

Answer 1

here is query that returns your values from a table with 3 columns:

select *
, to_char(gpa, '09.9') as gpa_text
, name || '-' || major || '-Grade' ||
case    when gpa between 3.5 and 4.0 then 'A'
    when gpa between 2.5 and 3.4 then 'B'
    when gpa between 1.5 and 2.4 then 'C'
    when gpa between 0.5 and 1.4 then 'D'
    else 'F' end
|| '-' || ltrim(to_char(gpa, '09.9')) as newfield
from students

This is working code, here is the newfield for Bob, "Bob-sci-GradeC-02.0"

I would strongly suggest that you do not have a text column in a database to hold a duplicate of a numeric value. I'm not quite sure why I need the ltrim, it seems odd that the formatted string would have a leading blank.