Do I need to use GROUP BY to do this?

[Grant Giddens]

Hi,

  I have a table where I keep sales transactions, so I'm trying to do a 
query that will count the number of transactions per day.

My test data looks like:

-- 
-- Table structure for table `sales_activity`
-- 

CREATE TABLE `sales_activity` (
  `sales_id` int(11) NOT NULL auto_increment,
  `sales_date` datetime NOT NULL default '0000-00-00 00:00:00',
  `sales_type` tinyint(4) NOT NULL default '0',
  PRIMARY KEY  (`sales_id`)
) ENGINE=MyISAM DEFAULT CHARSET=latin1 AUTO_INCREMENT=11 ;

-- 
-- Dumping data for table `sales_activity`
-- 

INSERT INTO `sales_activity` VALUES (1, '2008-06-15 13:00:00', 1);
INSERT INTO `sales_activity` VALUES (2, '2008-06-15 13:00:00', 1);
INSERT INTO `sales_activity` VALUES (3, '2008-06-15 13:00:00', 1);
INSERT INTO `sales_activity` VALUES (4, '2008-06-15 13:00:00', 1);
INSERT INTO `sales_activity` VALUES (5, '2008-06-15 13:00:00', 2);
INSERT INTO `sales_activity` VALUES (6, '2008-06-15 13:00:00', 2);
INSERT INTO `sales_activity` VALUES (7, '2008-06-16 13:00:00', 1);
INSERT INTO `sales_activity` VALUES (8, '2008-06-16 13:00:00', 1);
INSERT INTO `sales_activity` VALUES (9, '2008-06-17 13:00:00', 1);
INSERT INTO `sales_activity` VALUES (10, '2008-06-17 13:00:00', 1);
        

I would like to get a count of the number of transactions where transaction 
id=1 for each date.

ie, the result set should look like:

2008-06-15    4
2008-06-16    2
2008-06-17    2


What type of query do I need to get that information?

Thanks!