Postgres array lookup in WHERE clause

I have a query:

SELECT bar, (SELECT name FROM names WHERE value = bar) as name
FROM foobar WHERE foo = 1 and bar = ANY (1,2,3)

My problem is, when there is no row containing bar = 3 (or whatever other value is requested) in table foobar, no rows are returned for that value of bar.

I'd like my query to return a row of [bar, NULL] instead, but can't think up a way to approach this.

Is this e开发者_StackOverflow社区ven possible?

Perhaps something like this approach is what you are after:

testbed:

create view names as 
select 1 as value, 'Adam' as name union all select 2, 'Beth';

create view foobar as 
select 1 as foo, 1 as bar union all select 1, 2;

original method:

select bar, (select name from names where value = bar) as name 
from foobar 
where foo = 1 and bar = any (array[1, 2, 3]);

 bar | name
-----+------
   1 | Adam
   2 | Beth
(2 rows)

alternative method:

with w as (select unnest(array[1, 2, 3]) as bar)
select bar, (select name from names where value = bar) as name
from w left outer join foobar using(bar);

 bar | name
-----+------
   1 | Adam
   2 | Beth
   3 |
(3 rows)

If you are on 8.3 or before, there is no built-in unnest function, but you can roll your own (not very efficient) replacement:

create or replace function unnest(anyarray) returns setof anyelement as $$
  select $1[i] from generate_series(array_lower($1,1), array_upper($1,1)) i;
$$ language 'sql' immutable;

SELECT bar, name
FROM foobar
INNER JOIN names ON foobar.bar = names.value
WHERE foo = 1 and bar = ANY (1,2,3)

Try that query instead.

SELECT  vals.bar, name
FROM    (
        SELECT  *
        FROM    unnest([1, 2, 3]) AS bar
        ) vals
LEFT JOIN
        foobar
ON      foobar.foo = 1
        AND foobar.bar = vals.bar
LEFT JOIN
        names
ON      names.value = vals.bar