是否在SQL Server Management Studio 2016中旋转并添加新列？

Question

I have a database that looks like this:

IndexID QuestionID  AnswerGiven
1       3           Phone
1       7           Strongly Agree
2       8           Agree
2       5           Yes
2       3           Chat
3       6           NULL
3       3           Phone
4       3           Web
4       7           Disagree

And I want to write a script to essentially pull out Question #3 into its own column called ContactChannel, like this:

IndexID QuestionID  ContactChannel  AnswerGiven
1       7           Phone           Strongly Agree
2       8           Chat            Agree
2       5           Chat            Yes
3       6           Phone           Disagree
4       7           Web             Disagree

I'm new to SQL, but I suspect this has something to do with pivoting and sub-queries, and I know it can vary by database Any ideas for SSMS 2016?

Answer 1

You can use a query like the following:

SELECT t1.IndexID, t1.QuestionID, t2.AnswerGiven AS ContactChannel, t1.AnswerGiven
FROM mytable AS t1
LEFT JOIN mytable AS t2 ON t1.IndexID = t2.IndexID AND t2.QuestionID = 3
WHERE t1.QuestionID <> 3;

The query is in ANSI SQL and should work in any RBDMS.

Demo here

Answer 2

You can use max window function to do this, assuming there is one row per questionid=3 per indexid.

select * from (
select indexid,questionid,
max(case when questionid=3 then answergiven end) over(partition by indexid) as contactchannel,
answergiven
from tbl
) t
where questionid<>3