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Flatten Nested Data in SQL
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Flatten Nested Data in SQL

MediumSQL · PostgreSQL

Problem

Write a SQL query to flatten hierarchical or nested data into a tabular format.

Assume the input is represented by divisions, teams, and members, where teams belong to divisions and members may belong to teams. Preserve divisions and teams even when their child rows are absent.

Output

  1. One row per team-member combination, plus rows for divisions or teams without children.
  2. Return division_id, division_name, team_id, team_name, member_id, member_name, and member_role.
  3. Sort by division, team, and member identifiers, placing missing child rows last.

Schema

divisions
ColumnTypeDescription
division_idPKINTUnique division identifier
division_nameVARCHAR(100)Division name
teams
ColumnTypeDescription
team_idPKINTUnique team identifier
division_idINTParent division identifier
team_nameVARCHAR(100)Team name
members
ColumnTypeDescription
member_idPKINTUnique member identifier
team_idINTParent team identifier
member_nameVARCHAR(100)Member name
member_roleVARCHAR(100)Member role
Tablesdivisionsteamsmembers
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