1242 - Subquery returns more than 1 row

[Chevy Mark Sunderland]

Hello.
First of all I must say that I am a newbie when it comes to MySQL.
Here is my problem.
I need update the field `myNumberPreviousYear` of the table `tbl_x` with the value returned from query select count(*) in the table `tbl_z` for single field `myType` and where field `myArea`.
I try this update query and subquery but I have error: 1242 - Subquery returns more than 1 row
Can you help me?
Thanks for your time and hints.
Chevy

mysql> UPDATE `tbl_x` t
JOIN(
	SELECT
		(
			SELECT
				COUNT(*) AS `T`
			FROM
				`tbl_z`
			WHERE
				1
			AND `myDate` BETWEEN MAKEDATE(YEAR(CURDATE()) - 1, 1)
			AND MAKEDATE(YEAR(CURDATE()) - 1, 365)
			AND `myArea` = 'DX'
			GROUP BY
				`myType`
		)q
)x
SET t.myNumberPreviousYear = x.q
WHERE
	1
AND `myArea` = 'DX';
1242 - Subquery returns more than 1 row



mysql> select version();
+---------------------+
| version()           |
+---------------------+
| 5.0.45-community-nt |
+---------------------+
1 row in set




SET FOREIGN_KEY_CHECKS=0;
-- ----------------------------
-- Table structure for `tbl_z`
-- ----------------------------
DROP TABLE IF EXISTS `tbl_z`;
CREATE TABLE `tbl_z` (
  `myId` int(11) NOT NULL auto_increment,
  `myDate` date default NULL,
  `myArea` varchar(4) default NULL,
  `myType` varchar(50) default NULL,
  UNIQUE KEY `myId` (`myId`),
  KEY `myArea` (`myArea`),
  KEY `myType` (`myType`)
) ENGINE=MyISAM AUTO_INCREMENT=209 DEFAULT CHARSET=latin1;

-- ----------------------------
-- Records of tbl_z
-- ----------------------------
INSERT INTO tbl_z VALUES ('1', null, '2012-03-06', 'DX', 'C');
INSERT INTO tbl_z VALUES ('2', null, '2012-02-17', 'DX', 'E');
INSERT INTO tbl_z VALUES ('3', null, '2012-02-17', 'DX', 'E');
INSERT INTO tbl_z VALUES ('4', null, '2012-02-16', 'DX', 'F');
INSERT INTO tbl_z VALUES ('5', null, '2012-02-06', 'DX', 'F');
INSERT INTO tbl_z VALUES ('6', null, '2012-02-03', 'DX', 'D');
INSERT INTO tbl_z VALUES ('7', null, '2012-02-03', 'DX', 'F');
INSERT INTO tbl_z VALUES ('9', null, '2012-01-31', 'DX', 'A');
INSERT INTO tbl_z VALUES ('10', null, '2012-01-31', 'DX', 'D');





SET FOREIGN_KEY_CHECKS=0;
-- ----------------------------
-- Table structure for `tbl_x`
-- ----------------------------
DROP TABLE IF EXISTS `tbl_x`;
CREATE TABLE `tbl_x` (
  `myType` varchar(255) default NULL,
  `myNumberPreviousYear` int(10) default NULL,
  `myNumberPreviousMonthYear` int(10) default NULL,
  `myNumberCurrentYear` int(10) default NULL,
  `myChange` decimal(10,0) default NULL,
  `myArea` char(6) default NULL,
  `myId` int(10) NOT NULL auto_increment,
  PRIMARY KEY  (`myId`)
) ENGINE=MyISAM AUTO_INCREMENT=9 DEFAULT CHARSET=latin1 ROW_FORMAT=FIXED;

-- ----------------------------
-- Records of tbl_x
-- ----------------------------
INSERT INTO tbl_x VALUES ('A', null, null, null, null, 'DX', '1');
INSERT INTO tbl_x VALUES ('B', null, null, null, null, 'DX', '2');
INSERT INTO tbl_x VALUES ('C', null, null, null, null, 'DX', '3');
INSERT INTO tbl_x VALUES ('D', null, null, null, null, 'DX', '4');
INSERT INTO tbl_x VALUES ('E', null, null, null, null, 'DX', '5');
INSERT INTO tbl_x VALUES ('F', null, null, null, null, 'DX', '6');
INSERT INTO tbl_x VALUES ('G', null, null, null, null, 'DX', '7');
INSERT INTO tbl_x VALUES ('H', null, null, null, null, 'DX', '8');