Dynamic Pivot Query without storing query as String

问题

I am fully familiar with the following method in the link for performing a dynamic pivot query. Is there an alternative method to perform a dynamic pivot without storing the Query as a String and inserting a column string inside it?

http://www.simple-talk.com/community/blogs/andras/archive/2007/09/14/37265.aspx

回答1:

Short answer: no.

Long answer:

Well, that's still no. But I will try to explain why. As of today, when you run the query, the DB engine demands to be aware of the result set structure (number of columns, column names, data types, etc) that the query will return. Therefore, you have to define the structure of the result set when you ask data from DB. Think about it: have you ever ran a query where you would not know the result set structure beforehand?

That also applies even when you do select *, which is just a sugar syntax. At the end, the returning structure is "all columns in such table(s)".

By assembling a string, you dynamically generate the structure that you desire, before asking for the result set. That's why it works.

Finally, you should be aware that assembling the string dynamically can theoretically and potentially (although not probable) get you a result set with infinite columns. Of course, that's not possible and it will fail, but I'm sure you understood the implications.

Update

I found this, which reinforces the reasons why it does not work.

Here: