How to unite several tables in a one so the names of the columns became the row names? - sql

Question

for instance I have
SELECT customer_id, first_name || ', ' || last_name || ', ' || email as "customer's info"
FROM customer
WHERE customer_id = 5
;
SELECT count(i.film_id) AS "num.of films rented" FROM payment p
JOIN rental r ON p.rental_id = r.rental_id
JOIN inventory i ON r.inventory_id = i.inventory_id
WHERE r.rental_date >= ('2014-01-01'::date)
AND r.rental_date <= ('2017-05-03'::date)
AND p.customer_id = 5
;
I want in output
metric1 | metric2
----------------------------
customer's info | blalalalal
num.of films rented | blalalalal
I try smth like, but nothing
SELECT * FROM crosstab(
SELECT first_name || ', ' || last_name || ', ' || email
FROM customer WHERE customer_id = 5,
SELECT count(i.film_id) FROM payment p
JOIN rental r ON p.rental_id = r.rental_id
JOIN inventory i ON r.inventory_id = i.inventory_id
WHERE r.rental_date >= ('2014-01-01'::date)
AND r.rental_date <= ('2017-05-03'::date))
AS ('fjfjf' TEXT, 'fjfjf' int );
Could you help me?
I dont know how to do it in postgress
Thanks a lot

Answer 1

I would UNION ALL the two queries together - but remember to CAST the count value as a string, as you need matching data types to UNION:
SELECT
'customer''s info' AS "name"
, first_name || ', ' || last_name || ', ' || email AS "value"
FROM customer c
UNION ALL
'num.of films rented' AS "name"
, COUNT(i.film_id)::VARCHAR(5) AS "value"
FROM payment p
JOIN rental r ON p.rental_id = r.rental_id
JOIN inventory i ON r.inventory_id = i.inventory_id
WHERE r.rental_date >= ('2014-01-01'::date)
AND r.rental_date <= ('2017-05-03'::date)
WHERE customer_id = 5
;

Answer 2

It is unclear to me why inventory is in the second join.
SELECT 'customer''s info' as metric1,
first_name || ', ' || last_name || ', ' || email as metric2
FROM customer
WHERE customer_id = 5
UNION ALL
SELECT 'num.of films rented' as metric1, count(i.film_id)::text AS metric2
FROM payment p JOIN
rental r
ON p.rental_id = r.rental_id
WHERE r.rental_date >= '2014-01-01'::date AND
r.rental_date <= '2017-05-03'::date AND
p.customer_id = 5;
You could also combine this into a single query if you are just trying to get the results in a single result set:
SELECT (first_name || ', ' || last_name || ', ' || email) as customer_info,
count(i.film_id) as num_films
FROM payment p JOIN
rental r
ON p.rental_id = r.rental_id JOIN
customer c
ON c.customer_id = p.customer_id
WHERE r.rental_date >= '2014-01-01'::date AND
r.rental_date <= '2017-05-03'::date AND
c.customer_id = 5
GROUP BY c.customer_id;
(This puts the values in one row with two columns.) Using a subquery, the results can be easily unpivoted.