How create a column containing columns as values in redshift? - amazon-web-services

Question

I have a data like this below :
id start_date end_date col1 col2 col3 col4 col5
issue_2017-09 2017-09-18 2017-09-30 true true true true false
i want to convert data into the following format:
id start_date end_date new_col
issue_2017-09 2017-09-18 2017-09-30 {'col1', 'col2', 'col3', 'col4'}
new_col is created out of the columns [col1, col2, col3, col4, col5] which are true.
plus I am using redshift.

Answer 1

I was able to resolve this using the following query :
select id, start_date , end_date, listagg(col_name, ', ') as new_col
from (
select id, start_date, end_date, col1 as val, 'col1' as col_name
from table
union all
select id, start_date, end_date, col2 as val, 'col2' as col_name
from table
union all
select id, start_date, end_date, col3 as val, 'col3' as col_name
from table
union all
select id, start_date, end_date, col4 as val, 'col4' as col_name
from table
union all
select id, start_date, end_date, col5 as val, 'col5' as col_name
from table
) t
where val is True
group by id, start_date, end_date

Answer 2

Here is an alternative method,
select
id, start_date, end_date,
'{' +
case when col1 then '''col1''' else '' end +
case when col2 then case when col1 then ', ''col2''' else '''col2''' end else '' end +
case when col3 then case when (col1 or col2) then ', ''col3''' else '''col3''' end else '' end +
case when col4 then case when (col1 or col2 or col3) then ', ''col4''' else '''col4''' end else '' end +
case when col5 then case when (col1 or col2 or col3 or col4) then ', ''col5''' else '''col5''' end else '' end +
'}' as new_col
from table01;