UNION types double precision and character varying cannot be matched - postgresql

Question

I am trying to run a program from my following database
DATABASE
But i am getting the error "UNION types double precision and character varying cannot be matched" every time I try to run the program
My code is
SELECT
EXTRACT(YEAR
FROM AGE(users.dob)) AS Age,
users.gender,
app.name AS App
FROM users
LEFT OUTER JOIN app_user_profile
ON users.id = app_user_profile.users_id
LEFT OUTER JOIN app
ON app_user_profile.app_id = app.id
UNION
SELECT cities.name AS City, provinces.name AS Province, countries.name AS Country
FROM cities
LEFT OUTER JOIN provinces
ON cities.country_id = provinces.country_id
LEFT OUTER JOIN countries
ON provinces.country_id = countries.country_id

Answer 1

UNIONs in PostgreSQL must have the same number of columns and the columns must be of "compatible data types".
Judging from the names of your columns, these seem to be totally different things that you want to UNION. Which is unusual, but it can be done. The biggest problem seems to be between Age and City which are a number and text/varchar, respectively. If you cast Age as text, the UNION should work.
SELECT
EXTRACT(YEAR
FROM AGE(users.dob))::text AS Age,
....
Type casting can either be done with Column::<new type> or Cast(Column, <new type>). The first version is a custom PostgreSQL syntax and easy to type, and the second version conforms to SQL standards.