Question

我正在尝试按自动收报机，日期进行分组，并在不同的列中为不同的代码显示它们的值。但我不知道我桌子上的确切股票名称。原始表（代码可能有除A，B，C之外的其他符号）：

  date | ticker      | value
    -------------------------
     1 | A           | 5
     1 | B           | 3
     1 | C           | 2
     2 | A           | 5
     2 | B           | 3
     2 | C           | 2
     3 | A           | 5
     3 | B           | 3
     3 | C           | 2
.......

编写SQL查询以获取结果数据框：

  date | A           | B    | C
    --------------------------------
     1 | 5           | 3    | 2
     2 | 5           | 3    | 2
     3 | 5           | 3    | 2

Answer 1

正如sgeddes所说，这是通过一个支点完成的。当您不知道所有值时，可以动态创建一个轴。我举了一个这样做的例子

https://dba.stackexchange.com/questions/98776/dynamic-select-and-place-result-in-variable-columns/98809#98809

create Table  Questions
(
id int identity,
question_id int,
question_name varchar(255)
)
go

with CTEquestion
as
(
    select 1 QID
    union all
    Select QID+1
    from CTEquestion
    where QID < 11
)
insert questions
select QID, 'Question'+cast(QID as varchar(50))
from CTEquestion


insert QuestionAnswers
values ('2015-04-23', 'a1', 1, 'Canswer1')
    ,  ('2015-04-23', 'a1', 2, 'Ianswer2')
    ,  ('2015-04-23', 'a1', 3, 'Canswer3')
    ,  ('2015-04-23', 'a1', 4, 'Canswer4')
    ,  ('2015-04-23', 'a1', 5, 'Ianswer5')
    ,  ('2015-04-23', 'a1', 6, 'Ianswer6')
    ,  ('2015-04-23', 'a1', 7, 'Canswer7')
    ,  ('2015-04-23', 'a1', 8, 'Canswer8')
    ,  ('2015-04-23', 'a1', 9, 'Canswer9')
    ,  ('2015-04-23', 'a1', 10,'Canswer10')

insert QuestionAnswers
values (CONVERT(DATE, GETDATE()), 'b2', 1, 'Canswer1')
    ,  (CONVERT(DATE, GETDATE()), 'b2', 2, 'Canswer2')
    ,  (CONVERT(DATE, GETDATE()), 'b2', 3, 'Canswer3')
    ,  (CONVERT(DATE, GETDATE()), 'b2', 4, 'Canswer4')
    ,  (CONVERT(DATE, GETDATE()), 'b2', 5, 'Canswer5')
    ,  (CONVERT(DATE, GETDATE()), 'b2', 6, 'Ianswer6')
    ,  (CONVERT(DATE, GETDATE()), 'b2', 7, 'Canswer7')
    ,  (CONVERT(DATE, GETDATE()), 'b2', 8, 'Canswer8')
    ,  (CONVERT(DATE, GETDATE()), 'b2', 9, 'Canswer9')
    ,  (CONVERT(DATE, GETDATE()), 'b2', 10, 'Ianswer10')

insert QuestionAnswers
values (CONVERT(DATE, GETDATE()), 'c3', 1, 'Ianswer1')
    ,  (CONVERT(DATE, GETDATE()), 'c3', 2, 'Ianswer2')
    ,  (CONVERT(DATE, GETDATE()), 'c3', 3, 'Canswer3')
    ,  (CONVERT(DATE, GETDATE()), 'c3', 4, 'Ianswer4')
    ,  (CONVERT(DATE, GETDATE()), 'c3', 5, 'Canswer5')
    ,  (CONVERT(DATE, GETDATE()), 'c3', 6, 'Ianswer6')
    ,  (CONVERT(DATE, GETDATE()), 'c3', 7, 'Canswer7')
    ,  (CONVERT(DATE, GETDATE()), 'c3', 8, 'Canswer8')
    ,  (CONVERT(DATE, GETDATE()), 'c3', 9, 'Canswer9')
    ,  (CONVERT(DATE, GETDATE()), 'c3', 10, 'Ianswer10')

insert QuestionAnswers
values (CONVERT(DATE, GETDATE()), 'a1', 1, 'Canswer1')
    ,  (CONVERT(DATE, GETDATE()), 'a1', 2, 'Ianswer2')
    ,  (CONVERT(DATE, GETDATE()), 'a1', 3, 'Canswer3')
    ,  (CONVERT(DATE, GETDATE()), 'a1', 4, 'Canswer4')
    ,  (CONVERT(DATE, GETDATE()), 'a1', 5, 'Canswer5')
    ,  (CONVERT(DATE, GETDATE()), 'a1', 6, 'Canswer6')
    ,  (CONVERT(DATE, GETDATE()), 'a1', 7, 'Canswer7')
    ,  (CONVERT(DATE, GETDATE()), 'a1', 8, 'Canswer8')
    ,  (CONVERT(DATE, GETDATE()), 'a1', 9, 'Canswer9')
    ,  (CONVERT(DATE, GETDATE()), 'a1', 10, 'Ianswer10')
-->End test data creation

--straight join
select qa.user_id, qa.question_set, q.question_id, qa.answer
from Questions q
    join QuestionAnswers qa on qa.question_id=q.question_id
order by qa.user_id


--dynamic pivot 
DECLARE 
    @questionList varchar(max)
, @maxQID int
, @qid int

select @questionList='',@maxQID = MAX(question_id), @qid= MIN(question_id)
FROM Questions

while @qid <= @maxQID
begin
    set @questionList=@questionList+'['+cast(@qid as varchar(10))+']'

    select @qid=min(question_id)
    from Questions
    where question_id > @qid

    if @qid<=@maxQID
        set @questionList=@questionList+', '
end

DECLARE @SQL NVARCHAR(MAX)

SET @SQL = N'
select user_id, '+@questionList+'
from
(select q.question_id, qa.question_set, qa.user_id, qa.answer
from Questions q
    join QuestionAnswers qa on qa.question_id=q.question_id) x
PIVOT
(
max(answer)
FOR question_id in ('+@questionList+')
) pvt
order by user_id'

exec sp_executesql @SQL

Answer 2

如果您知道自动收报机价值，则可以执行GROUP BY。使用CASE执行条件SUM：

select date,
       SUM(case when ticker = 'A' then value end) as A,
       SUM(case when ticker = 'B' then value end) as B,
       SUM(case when ticker = 'C' then value end) as C,
       ...
from tablename
group by date

核心ANSI SQL-99。

如果不同的股票代码值未知，并且可能在执行之间发生变化，则您需要特定于产品的功能。（一般行为是SELECT始终返回相同数量的列 - 与表数据无关！）

SQL查询：在不同的列中显示不同的组值

2 个答案: