how to get vistors_sum and reviews_count in 3 table? - mysql

Question

how to get vistors_sum and reviews_count in 3 table ?
see the bellow codes, how to get my result in one sql?
SET FOREIGN_KEY_CHECKS=0;
-- ----------------------------
-- Table structure for `a`
-- ----------------------------
DROP TABLE IF EXISTS `a`;
CREATE TABLE `a` (
`products_id` int(11) NOT NULL,
`products_name` varchar(255) default NULL,
PRIMARY KEY (`products_id`)
) ENGINE=MyISAM DEFAULT CHARSET=utf8;
-- ----------------------------
-- Records of a
-- ----------------------------
INSERT INTO `a` VALUES ('1', 'jimmy');
INSERT INTO `a` VALUES ('2', 'tina');
INSERT INTO `a` VALUES ('3', 'emma');
SET FOREIGN_KEY_CHECKS=0;
-- ----------------------------
-- Table structure for `b`
-- ----------------------------
DROP TABLE IF EXISTS `b`;
CREATE TABLE `b` (
`id` int(11) NOT NULL auto_increment,
`products_id` int(11) NOT NULL,
`vistors` int(11) NOT NULL,
`date` date default NULL,
PRIMARY KEY (`id`)
) ENGINE=MyISAM AUTO_INCREMENT=5 DEFAULT CHARSET=utf8;
-- ----------------------------
-- Records of b
-- ----------------------------
INSERT INTO `b` VALUES ('1', '1', '1', '2013-11-13');
INSERT INTO `b` VALUES ('2', '1', '2', '2013-11-04');
INSERT INTO `b` VALUES ('3', '2', '1', '2013-11-13');
INSERT INTO `b` VALUES ('4', '2', '3', '2013-11-13');
SET FOREIGN_KEY_CHECKS=0;
-- ----------------------------
-- Table structure for `c`
-- ----------------------------
DROP TABLE IF EXISTS `c`;
CREATE TABLE `c` (
`id` int(11) NOT NULL auto_increment,
`products_id` int(11) NOT NULL,
`review_content` varchar(255) default NULL,
`date` date default NULL,
PRIMARY KEY (`id`)
) ENGINE=MyISAM AUTO_INCREMENT=5 DEFAULT CHARSET=utf8;
-- ----------------------------
-- Records of c
-- ----------------------------
INSERT INTO `c` VALUES ('1', '1', 'hello', '2013-11-13');
INSERT INTO `c` VALUES ('2', '1', 'world', '2013-11-13');
INSERT INTO `c` VALUES ('3', '2', 'good', '2013-11-12');
INSERT INTO `c` VALUES ('4', '3', 'boy', '2013-11-13');
this code bellow can do but the date condition is in sub children temp table. this make the sql not flexible (if I want to query any time not 2013-11-13)
select
a.products_id,
a.products_name,
b.vistors_sum,
c.reviews_count
from
a
left join
(
select
b.products_id,
b.date,
sum(b.vistors) as vistors_sum
from b
where b.date = '2013-11-13'
group by b.products_id
) as b on a.products_id = b.products_id
left join
(
select
c.products_id,
count(c.products_id) as reviews_count
from c
where c.date = '2013-11-13'
group by c.products_id
) as c on a.products_id = c.products_id

Answer 1

SQLFiddle demo
select a.products_id,
products_name,
COALESCE(b.sum_visitors,0) as sum_visitors,
COALESCE(c.count_comments,0) as count_comments
from a
left join
( SELECT products_id,sum(vistors) as sum_visitors
FROM b
WHERE date='2013-11-13'
GROUP BY products_id
) as b
on (a.products_id=b.products_id)
left join
(
SELECT products_id,count(*) as count_comments
FROM c
WHERE date='2013-11-13'
GROUP BY products_id
) as c
on (a.products_id=c.products_id)