Update rows in table with set-returning function I am trying to update a table of 100 already existing rows with 100 random values from a Gaussian distribution, for which I am using the normal_rand function from the tablefunc extension. Since this is a set-returning function I placed it it the FROM-clause.

UPDATE foo
SET bar = r
FROM normal_rand(100, 0, 1) AS r;


However, when executing the statement, all rows in the table are assigned the same value (presumably the first), as such:

bar
-------
0.2451
0.2451
0.2451
...
0.2451


I also tried generate_series, but this yields similar results. How can I assign the first value of normal_rand(100, 0, 1) to the first row, the second to the second etc.?
This is not going to be fast, but you need a subquery that assigns row numbers for each row that can be used for joining the generated values with the table. You can use with ordinality to generate such number for the result of a set-returning function. 

with numbered as (
  select id, 
         row_number() over (order by id) as rn
  from foo 
)
update foo
  set r = t.val
from (
  select n.id,
         nr.val
  from numbered n
    join normal_rand(1000, 5, 3) with ordinality nr(val,idx) on n.rn = nr.idx
) t
where t.id = foo.id


Replace id with the primary key column of your table.

Online example