语法易错点

1. 创建临时表

with tmp as 
    (select ... from ...)
select ... from ...

--创建单个临时表后，重新书写查询语句时，无需逗号隔开。

with tmp1 as
    (select ... from ...),
with tmp2 as
    (select ... from ...)

--创建多个临时表时，需逗号分隔。

2. 选择分支

case when ... then '...'
    when ... then '...'
    else ... end as ...

--多分支无需逗号分隔，注意单引号位置。

3. 窗口函数

... over(partition by ... order by ...)

--注意括号内的语法顺序。

... over(order by rows between unbounded preceding and current row)
... over(rows between unbounded preceding and unbounded following)

--注意 order by、rows between 缺省时，rows between 的默认值。