Question

Which of the following is a query that you CANNOT write in Standard SQL over a table that encodes the Parent relationship:

Parent(ChildID, ParentID)

The ParentID and ChildID both come from the set of universal IDs for people (e.g., National Insurance number), and a row having {ChildID = X, ParentID = Y} indicates that Y (the holder of the ID# Y) is the parent of X.

A. Find Parent of X
B. Find Children of X
C. Find all Ancestors of X
D. Find all Parents and Grandparents of X

Answer 1

the query which is not possible is Find all Ancestors of X because in standard SQL query we can have nested queries but to find the ancestors we do not know how many ancestors will be there so we do not know many nested inner queries we have to write for it, so it is not possible in standard SQL query.

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