How can I show the counts of distinct values and include zeros?

Question

I have a simple MySQL DB with the following fields:

mysql> SELECT * from table;
+----+-----------+------+
| id | location  | name | 
+----+-----------+------+
|  1 | NJ        | Gary |
|  2 | MN        | Paul |
|  3 | AZ        |      |
|  4 | MI        | Adam |
|  5 | NJ        |      |
|  6 | MN        | Dave |
+----+-----------+------+
6 rows in set (0.00 sec)

I need to retrieve a list of how many people are from each state, excluding those who don't have a name. In other words, I'm trying to reproduce the following result:

+----------+-------+
| location | count | 
+----------+-------+
| AZ       |     0 |
| MI       |     1 |
| MN       |     2 |
| NJ       |     1 |
+----------+-------+

I'm able to get close with

SELECT location, COUNT(*) AS count FROM table WHERE name!='' GROUP BY location;

However, COUNT(*) excludes the zero counts. I attempted to use JOIN along with the table produced by

SELECT DISTINCT location, null as count from table;

but a LEFT JOIN throws out the count column from the right table, and a RIGHT JOIN doesn't seem to include the zero rows or the actual counts for some reason.

I feel as though there's a MySQL command or something simple that I'm missing. I just need to find a way to merge the two tables based on location.

Can anybody point me in the right direction?

Answer 1

COUNT will return number of non-null values, so you need a way to convert empty strings to nulls to get 0s.

 SELECT location, COUNT(NULLIF(name,'')) AS count FROM table GROUP BY location;