PostgreSQL - Using a Subquery to Update Multiple Column Values

Question

I need to be able to update multiple columns on a table using the result of a subquery. A simple example will look like below -

UPDATE table1
SET (col1, col2) =         


        

Answer 1

If you want to avoid two subselects, the query can be rewritten like this:

UPDATE table1
  SET col1 = o_min, col2 = o_max
FROM ( 
    SELECT min(ship_charge) as o_min, 
           max(ship_charge) as o_max
    FROM orders
) t 
WHERE col4 = 1001

If ship_charge is not indexed, this should be faster than two subselects. If ship_charge is indexed, it probably doesn't make a big difference

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Edit

Starting with Postgres 9.5 this can also be written as:

UPDATE table1
  SET (col1, col2) = (SELECT min(ship_charge), max(ship_charge) FROM orders)
WHERE col4 = 1001