Postgresql/SQL insert into table based on multiple column values - sql

Question

My origin table looks like this
company_name | feature_name | feature_value
abc | income | 315
abc | cash | 213
abc | val | 9
goo | income | 123
goo | cash | 487
goo | val | 990
I want to insert into a new table so that the new table looks like this, and the new table won't contain column for cash.
company_name | income_name | income_value | val_name | val_value
abc | income | 315 | val | 9
goo | income | 123 | val | 990
I've checked a lot of posts but still don't know how to do that. Any suggestion is appreciated.

Answer 1

To pivot data without using any proprietary syntax you have a couple of options. Group/max on conditionals or left join multiple times:
SELECT
company_name,
MAX(CASE WHEN feature_name = 'income' THEN feature_value END as income,
MAX(CASE WHEN feature_name = 'val' THEN feature_value END as val,
...
FROM
table
GROUP BY company name
To see how it works run it without the group by and max operations; you'll see how the case when spreads the single value column out into multiple columns, multiple rows per company. The group by and max collapse these multiple rows to a single row by removing all the nulls
If your table is just a snippet you can add more columns where the ... is by copying the pattern. Remember to remove the trailing comma from the select list items
The join way:
SELECT
t.company_name,
income.feature_value as income,
val.feature_value as val,
...
FROM
table t
LEFT JOIN table income ON t.company_name = income.company_name and income.feature_name = 'income'
LEFT JOIN table val ON t.company_name = val.company_name and val.feature_name = 'val'
...
This virtually splits the table into multiple tables each having the company name and just some of the rows, making a table per feature, then joins them all back together into one multi column result set
I've always preferred the group way but you'd have to trial which was more efficient for your situation and which is easier to maintain for your understanding
Inserting data from a select into another table is a very common operation so I've omitted that part for clarity- this is just to show you how to pivot the data. The insert will be one of:
INSERT INTO existingtable(company_name, income, val)
SELECT ...
CREATE newtable AS
SELECT ...

Answer 2

You can try with conditional aggregation using case when expression
select company_name,
max(case when feature_name='income' then feature_name end) as income_name,
max(case when feature_name='income' then feature_name end) as income_value,
max(case when feature_name='val' then feature_name end) as val_name,
max(case when feature_name='val' then feature_name end) as val_value
from tablename
group by company_name