小编Roh*_*han的帖子

请帮我解决这个问题:给你一个表,包含两列:列是以下之一:

Doctor
Professor
Singer
Actor

编写查询以输出相应occ下面的名称.采用以下格式:

+--------+-----------+--------+------+

| Doctor | Professor | Singer | Actor|

+--------+-----------+--------+------+

名称必须按字母顺序排列.

样本输入

Name        Occupation
Meera       Singer
Ashely      Professor
Ketty       Professor
Christeen   Professor
Jane        Actor
Jenny       Doctor
Priya       Singer    

样本输出

Jenny    Ashley     Meera  Jane

Samantha Christeen  Priya  Julia

NULL     Ketty      NULL   Maria

注意

当没有更多名称对应于职业时,打印"NULL".

我试过用:

SELECT *
FROM
(
SELECT [Name], [Occupation] 
FROM occupations 
) AS source
PIVOT
(
    max([Name])
    FOR [occupation] IN ([Doctor], [Professor], [Singer], [Actor]) 
) as pvt;

它给出了以下输出:

Priya Priyanka Kristeen Samantha …

a?: string和a: ?stringFlow 之间有什么区别？

function concat(a: ?string, b: ?string): string {
}

与

function concat(a?: string, b?: string): string {
}