distinct 和 order by
问题描述：
有两个sql，我以为查询结果会一样，但是结果却是天差地别：
第一条语句：
select distinct(ic.companyId) as companyId from industry_company ic join funding f on f.companyId=ic.companyId join company c on c.id = ic.companyId where (c.active = 'Y' or c.active is null) and (ic.active='Y' or ic.active is null) and (f.active is null or f.active='Y') and ic.industryId = 387 order by f.publishDate desc, f.fundingDate desc limit 5;
查询结果：
companyId |
+-----------+
| 352295 |
| 348968 |
| 270596 |
| 328046 |
| 246927 |
+---------
第二条语句：
select distinct(ic.companyId) as companyId, f.publishDate as date from industry_company ic join funding f on f.companyId=ic.companyId join company c on c.id = ic.companyId where (c.active = 'Y' or c.active is null) and (ic.active='Y' or ic.active is null) and (f.active is null or f.active='Y') and ic.industryId = 387 order by f.publishDate desc, f.fundingDate desc limit 5;
执行结果变了：
companyId | date |
+-----------+---------------------+
| 143467 | 2018-04-20 11:18:18 |
| 234394 | 2018-04-04 15:04:00 |
| 352295 | 2018-02-24 08:00:00 |
| 348968 | 2018-02-09 08:50:33 |
| 347770 | 2018-02-05 11:14:00 |
可以看到 companyId 列表 差异很大 ， 解释起来原因如下：
1、 distinct 会作用其后所有列
2、distinct 里如果缺乏ordey by 的字端，那么order by 没有作用
先distinct 后order by ，如果distinct 缺乏 order by 里面的字段，那么 该如何排序呢！
下面是SELECT语句的逻辑执行顺序：
1、FROM
2、ON
3、JOIN
4、WHERE
5、GROUP BY
6、WITH CUBE or WITH ROLLUP
7、HAVING
8、SELECT
9、DISTINCT
10、ORDER BY
11、TOP