Question

I have a Question and Answer table in SQL Server 2008 R2.

Question:

q_id
question_text

Answer:

a_id
question_text
answer_text

This is obviously bad design. The question_text field is duplicated in the Question and Answer tables and there is no foreign key relationship between Answer and Question. I want to create this relation by finding the Question (the q_id) for each Answer that is already present in the Answer table. I would do this by matching the question_text value that is copied to the Answer table to the rows in the Question table.

This is what I’d like to do in pseudo code.

• create a nullable q_id field in the Answer table (nullable because there is already data in the Answer table)
• select everything from the Answer table.
• for each row in the result
  — select the corresponding question from the Question table by comparing the question_text value.
  — insert the q_id into the nullable q_id column in the Answer table
• change the q_id column in the Answer to not nullable.

Could you help me achieve this in SQL Server 2008 R2? Thanks.

PS: All question_text values in the Question table are unique.

Answer 1

Try to:

select a.a_id, q.q_id, a.answer_text
    into NewAnswer
    from Answer a, Question q
    where a.question_text = q.question_text;

Once done, add constraints on NewAnswer, rename Answer to something else and NewAnswer to Answer.

[edit: fix syntax, according to this link]