SQL99 和 SQL92 的区别

这里主要说一下两者关于JOIN方面的区别：

SQL 92

select 
  e.*, 
  d.dname, 
  c.cname 
from 
  emp e, 
  dept d, 
  city c 
where 
  (
    e.deptno = d.deptno 
    and d.loc = c.cid 
    and sal > 2000
  ) 
  or (
    e.deptno = d.deptno 
    and d.loc = c.cid 
    and comm is not null
  ) 
order by 
  e.sal

SQL 99

select 
  * 
from 
  emp e 
  inner join dept d on e.deptno = d.deptno 
  inner join city c on d.loc = c.cid 
where 
  e.sal > 2000 
  or e.comm is not null 
order by 
  e.sal

我个人建议多表连接使用 SQL99 标准，因为层次性更强，可读性更强。