SQL Melt after Mapping Columns - sql

Question

I have the following working query:
SELECT
postgres."week" AS "week",
CASE
WHEN (postgres."spent_money_office") = 1 THEN (postgres."weight")
WHEN (postgres."spent_time_office") = 1 THEN (postgres."weight")
WHEN (postgres."spent_other_office") = 1 THEN (postgres."weight")
ELSE 0
END AS "office_leisure",
CASE
WHEN (postgres."spent_money_home") = 1 THEN (postgres."weight")
WHEN (postgres."spent_time_home") = 1 THEN (postgres."weight")
WHEN (postgres."spent_other_home") = 1 THEN (postgres."weight")
ELSE 0
END AS "home_leisure",
CASE
WHEN (postgres."spent_money_vacation") = 1 THEN (postgres."weight")
WHEN (postgres."spent_time_vacation") = 1 THEN (postgres."weight")
WHEN (postgres."spent_other_vacation") = 1 THEN (postgres."weight")
ELSE 0
END AS "vacation_leisure"
FROM
"lake"."postgres" AS "postgres"
GROUP BY
1,
2,
3,
4
ORDER BY
1
Which gives 4 columns: week, office_leisure, home_leisure, and vacation_leisure as shown here:
I would like to "melt" the leisure columns into one called leisure_type taking on 3 values, either office/home/vacation and another column called weight. How can this be done using the SQL code query above?
Something like:
week
leisure_type
weight
week 1
office
1.78
week 1
home
1.78
week 1
vacation
1.78
week 1
office
0
...
...
...

Answer 1

You can apply a union over the selection of the week, leisure type and leisure value, for each leisure type you have (so three times):
SELECT week,
'office_leisure' AS leisure_type,
office_leisure AS weight
FROM tab
UNION
SELECT week,
'home_leisure' AS leisure_type,
home_leisure AS weight
FROM tab
UNION
SELECT week,
'vacation_leisure' AS leisure_type,
vacation_leisure AS weight
FROM tab
You can find a fiddle here.