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Detect Missing or Duplicate Primary Keys
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Detect Missing or Duplicate Primary Keys

MediumSQL · PostgreSQL

Problem

Write a SQL query to identify records with missing or duplicate primary keys.

Use the qa_import_records table. Return each problematic record_id once, including a count and an issue classification. NULL record_id values represent missing keys and must be included. Order missing keys first, followed by duplicate keys in ascending key order.

Output

  1. Columns: record_id, record_count, and issue_type
  2. One row per missing or duplicated key
  3. issue_type must be MISSING or DUPLICATE

Schema

qa_import_records
ColumnTypeDescription
record_idINTEGERCandidate record identifier imported from the source system
source_rowPKINTEGERUnique row number assigned during the import
test_nameVARCHAR(150)Name of the QA test record
source_systemVARCHAR(100)System that supplied the imported record
Tablesqa_import_records
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