Update or Insert (multiple rows and columns) from subquery in PostgreSQL

Question

I'm trying to do something like this in postgres:

• UPDATE table1 SET (col1, col2) = (SELECT col2, col3 FROM othertable WHERE othertable.col1 = 123);

• INSERT INTO table1 (col1, col2) VALUES (SELECT col1, col2 FROM othertable)

But point 1 is not possible even with postgres 9.0 as mentioned in the docs (http://www.postgresql.org/docs/9.0/static/sql-update.html)

Also point 2 seems not working. i'm getting the following error: subquery must return only one column.

Hope somebody has a workaround for me. otherwise the queries will take a looot of time :(.

FYI: I'm trying to select different columns from several tables and store them into a temporary table, so that another application can easily fetch the prepared data.

Expulsive

Answer 1

For the UPDATE

Use:

UPDATE table1 
   SET col1 = othertable.col2,
       col2 = othertable.col3 
  FROM othertable 
 WHERE othertable.col1 = 123;

For the INSERT

Use:

INSERT INTO table1 (col1, col2) 
SELECT col1, col2 
  FROM othertable

You don't need the VALUES syntax if you are using a SELECT to populate the INSERT values.

Alcoholic

Is it possible to combine Update & Insert so that if one fails, the other will be used without throwing an error (independently for each row). I think that would be a more complete solution to the question (for example: https://mcmap.net/q/53809/-insert-on-duplicate-update-in-postgresql) – Barroom

Answer 2

OMG Ponies's answer works perfectly, but just in case you need something more complex, here is an example of a slightly more advanced update query:

UPDATE table1 
SET col1 = subquery.col2,
    col2 = subquery.col3 
FROM (
    SELECT t2.foo as col1, t3.bar as col2, t3.foobar as col3 
    FROM table2 t2 INNER JOIN table3 t3 ON t2.id = t3.t2_id
    WHERE t2.created_at > '2016-01-01'
) AS subquery
WHERE table1.id = subquery.col1;

Jordanson

perfect. this works best wherein you need to pick a subset based on a condition involving the updated table itself. – Chabazite

@David Namenyi can you explain this query? – Ophthalmologist

Answer 3

UPDATE table1 SET (col1, col2) = (col2, col3) FROM othertable WHERE othertable.col1 = 123;

Pasquale