MySQL巧用sum、case和when优化统计查询

CREATE TABLE `statistic_order` (
 `oid` bigint(20) NOT NULL,
 `o_source` varchar(25) DEFAULT NULL COMMENT '来源编号',
 `o_actno` varchar(30) DEFAULT NULL COMMENT '活动编号',
 `o_actname` varchar(100) DEFAULT NULL COMMENT '参与活动名称',
 `o_n_channel` int(2) DEFAULT NULL COMMENT '商城平台',
 `o_clue` varchar(25) DEFAULT NULL COMMENT '线索分类',
 `o_star_level` varchar(25) DEFAULT NULL COMMENT '订单星级',
 `o_saledep` varchar(30) DEFAULT NULL COMMENT '营销部',
 `o_style` varchar(30) DEFAULT NULL COMMENT '车型',
 `o_status` int(2) DEFAULT NULL COMMENT '订单状态',
 `syctime_day` varchar(15) DEFAULT NULL COMMENT '按天格式化日期',
 PRIMARY KEY (`oid`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8

select S.syctime_day,
 (select count(*) from statistic_order SS where SS.syctime_day = S.syctime_day and SS.o_source = 'CDE') as 'CDE',
 (select count(*) from statistic_order SS where SS.syctime_day = S.syctime_day and SS.o_source = 'CDE') as 'SDE',
 (select count(*) from statistic_order SS where SS.syctime_day = S.syctime_day and SS.o_source = 'CDE') as 'PDE',
 (select count(*) from statistic_order SS where SS.syctime_day = S.syctime_day and SS.o_source = 'CDE') as 'CSE',
 (select count(*) from statistic_order SS where SS.syctime_day = S.syctime_day and SS.o_source = 'CDE') as 'SSE'
 from statistic_order S where S.syctime_day > '2016-05-01' and S.syctime_day < '2016-08-01' 
 GROUP BY S.syctime_day order by S.syctime_day asc;

 select S.syctime_day,
 sum(case when S.o_source = 'CDE' then 1 else 0 end) as 'CDE',
 sum(case when S.o_source = 'SDE' then 1 else 0 end) as 'SDE',
 sum(case when S.o_source = 'PDE' then 1 else 0 end) as 'PDE',
 sum(case when S.o_source = 'CSE' then 1 else 0 end) as 'CSE',
 sum(case when S.o_source = 'SSE' then 1 else 0 end) as 'SSE'
 from statistic_order S where S.syctime_day > '2015-05-01' and S.syctime_day < '2016-08-01' 
 GROUP BY S.syctime_day order by S.syctime_day asc;