How to use the output of select query as an input in the insert query?

Question

I have following two tables:-

postgres=# select * from district;
 id |   name
----+-----------
  1 | Ahmedabad
  2 | Barmer
(2 rows)

postgres=# select * from wa         


        

Answer 1

Vao Tsun has the correct answer for using insert . . . select (and duly upvoted).

However, you are trying to use a subquery in values(). That is allowed, but a subquery needs its own parentheses. So your version would work as:

insert into warehouse (name, district_id)
    values ( 'Ghodasar-WH', (select id from district where name = 'Ahmedabad') );

Answer 2

try:

insert into warehouse
(name, district_id)
select 'Ghodasar-WH',id from district where name = 'Ahmedabad';

https://www.postgresql.org/docs/current/static/sql-insert.html

{ DEFAULT VALUES | VALUES ( { expression | DEFAULT } [, ...] ) [, ...] | query }

so just use query here