how to get all data from left table in a join

Question

say I have a table with names:

ID	Name
1	Carl
2	Mark

then I have another table where names.id is used

id	namesid	amount
1	1	100
2	1	50

My query is

SELECT names.id, names.name, IFNULL(sum(amount),'0,00') as sum_amount 
FROM names LEFT OUTER JOIN other_table ON names.id=other_table.namesid 
GROUP BY names.id 
WITH ROLLUP

but this query is returning no data for name.id=2. The expected result considering how I get that LEFT OUTER JOIN works is the following:

ID	Name	sum_amount
1	Carl	150
2	Mark	0,00

Why is it not working as expected? It should work also if there are no data in other_table ending with:

ID	Name	sum_amount
1	Carl	0,00
2	Mark	0,00

Answer 1

Your GROUP BY is incomplete and you do not need WITH ROLLUP

SELECT names.id, names.name, IFNULL(sum(amount),'0.00') as sum_amount 
FROM names LEFT OUTER JOIN other_table ON names.id=other_table.namesid 
GROUP BY names.id,names.name;

Here is a sample to prove it

mysql> DROP DATABASE IF EXISTS faieta;
Query OK, 1 row affected (0.05 sec)

mysql> CREATE DATABASE faieta;
Query OK, 1 row affected (0.00 sec)

mysql> USE faieta
Database changed
mysql> CREATE TABLE names (
    ->    id INT NOT NULL AUTO_INCREMENT,
    ->    name VARCHAR(20),
    ->    PRIMARY KEY (id)
    -> );
Query OK, 0 rows affected (0.01 sec)

mysql> INSERT INTO names (name) VALUES ('Carl');
Query OK, 1 row affected (0.00 sec)

mysql> INSERT INTO names (name) VALUES ('Mark');
Query OK, 1 row affected (0.00 sec)

mysql> CREATE TABLE other_table (
    ->    id INT NOT NULL AUTO_INCREMENT,
    ->    namesid INT NOT NULL,
    ->    amount DOUBLE,
    ->    PRIMARY KEY (id)
    -> );
Query OK, 0 rows affected (0.01 sec)

mysql> INSERT INTO other_table (namesid,amount) VALUES (1,100);
Query OK, 1 row affected (0.00 sec)

mysql> INSERT INTO other_table (namesid,amount) VALUES (1,50);
Query OK, 1 row affected (0.01 sec)

mysql>

Here is the query output

mysql> SELECT names.id, names.name, IFNULL(sum(amount),'0.00') as sum_amount
    -> FROM names LEFT OUTER JOIN other_table ON names.id=other_table.namesid
    -> GROUP BY names.id,names.name;
+----+------+------------+
| id | name | sum_amount |
+----+------+------------+
|  1 | Carl | 150        |
|  2 | Mark | 0.00       |
+----+------+------------+
2 rows in set (0.00 sec)

mysql>