Question

I have two database tables, ‘Lists’ and ‘Notes’.
Lists has columns _id, listname
Notes has columns _id, checked, list_id (which is a foreign key of Lists._id), and more columns that aren’t relevant to this question.

I would like to create a query that returns four columns:
Lists._id, Lists.listname, the count of all checked Notes in this list, the count of all Notes in this list.

The query should return all entries from Lists.

I can get the counts and the _ids & listnames seperately, using the following queries

SELECT _id, listname FROM Lists
SELECT count(checked) FROM Notes WHERE checked='1' and list_id=foo_id
SELECT count(*) FROM Notes WHERE list_id=foo_id

In these statements, foo_id refers to the _id of the list I would like to count checked and total items for.

Could someone show me how I could put these all into one query?

Bonus points for throwing an AS in there for the count columns.

Answer 1

EDIT: Added IFNULL to return 0 as count_checked when outer join returns no rows; added aliases.

SELECT
  l._id,
  l.listname,
  IFNULL( SUM(n.checked), 0 ) AS count_checked,
  COUNT(*) AS count_total
FROM lists l
LEFT OUTER JOIN notes n ON ( l._id = n.list_id )
GROUP BY l._id, l.listname