Select query to retrieve rows with null values I need to retrieve data from a table even if one of the fields has null value. Here's an example:

Select name, SUM(credit) as credit
From expenses
Where name like 'vendor0%'
and date like '2013%'
Group by name
Order by name asc


This example retrieves name and SUM(credit) only when credit has values. I need to retrieve all from name even if credit has no value at all.

Is this possible?
This example retrieves only "name" and the "SUM(credit)", when the
  "credit" has values.


The query you presented will retrieve a row for every present name, even if all associated credit columns are NULL. You get a row with a NULL value for SUM(credit) then. Null values are just ignored by the aggregate function sum():

You only get no row for a particular name if no row for that name exists in the table expenses for the given WHERE expressions.

I am assuming you want
.. only names matching 'vendor0%'
.. but all of those, even if they have no expenses in 2013.

Your query could work like this:

SELECT name, SUM(CASE WHEN date LIKE '2013%' THEN credit END) AS credit
FROM   expenses
WHERE  name LIKE 'vendor0%'
GROUP  BY name
ORDER  BY name


CASE defaults to NULL if no ELSE branch is given.
Aside: You shouldn't store date / time values as text. Use an appropriate type, it has many advantages.
And don't use "name" or "date" as identifiers. "name" is not a descriptive name and "date" is a reserved word in standard SQL and a function and base type name in Postgres.