Difference of averages of columns in 2 tables in Postgres database - postgresql

Question

I have split a table into 2 based on the average value of a column and now I want to calculate the difference in the average of the other columns in the new tables.
e.g. (simplified example, my data has 5 columns)
t1 = 'id', 'price', 'size'
1 , 10.0, 3
..., ..., ...
10, 6.50, 8
t2 = 'id', 'price', 'size'
11 , 12.12, 3
..., ..., ...
20, 3.50, 5 '
diff_table = 'diff_price' ,'diff_size'
t1.avg_price - t2.avg_price, t1.avg_size - t2.avg_size

Answer 1

Hm, pretty simple as:
SELECT
avg(t1.price) - avg(t2.price) AS diff_price,
avg(t1.size) - avg(t2.size) AS diff_size
FROM t1, t2;
Example: https://www.db-fiddle.com/f/eXuc1bUyxAHhWo2Yu91GMt/0
If you need that data to be put into a new table, just do the following )with explicit column typescale):
CREATE TABLE diff_table AS
SELECT
(avg(t1.price) - avg(t2.price))::decimal(10,2) AS diff_price,
(avg(t1.size) - avg(t2.size))::decimal(10,2) AS diff_size
FROM t1, t2;
...result:
Table "public.diff_table"
Column | Type | Collation | Nullable | Default
------------+---------------+-----------+----------+---------
diff_price | numeric(10,2) | | |
diff_size | numeric(10,2) | | |

Answer 2

Okay, I resolved my own problem.
CREATE TABLE diff AS
SELECT AVG(bathroomcnt) AS avg_bathroomcnt,
AVG(bedroomcnt) AS avg_bedroomcnt,
AVG(calculatedfinishedsquarefeet) AS avg_calculatedfinishedsqrft,
AVG(garagecarcnt) AS avg_garagecarcnt,
AVG(lotsizesquarefeet) AS avg_lotsizesqft,
AVG(roomcnt) AS avg_roomcnt
FROM higher_values;
CREATE TABLE diff2 AS
SELECT AVG(bathroomcnt) AS avg_bathroomcnt,
AVG(bedroomcnt) AS avg_bedroomcnt,
AVG(calculatedfinishedsquarefeet) AS avg_calculatedfinishedsqrft,
AVG(garagecarcnt) AS avg_garagecarcnt,
AVG(lotsizesquarefeet) AS avg_lotsizesqft,
AVG(roomcnt) AS avg_roomcnt
FROM lower_values;
SELECT h.avg_bathroomcnt - l.avg_bathroomcnt AS bathroomcnt_diff,
h.avg_bedroomcnt - l.avg_bedroomcnt AS bedroomcnt_diff,
h.avg_calculatedfinishedsqrft - l.avg_calculatedfinishedsqrft AS calculatedfinished_diff,
h.avg_garagecarcnt - l.avg_garagecarcnt AS garagecarcnt_diff,
h.avg_lotsizesqft - l.avg_lotsizesqft AS lotsizesqft_diff,
h.avg_roomcnt - l.avg_roomcnt AS roomcnt_diff
from diff as h, diff2 as l;