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Average Defects Over Time

HardSQL · PostgreSQL00:00
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Your question is Average Defects Over Time. Start with the requirements and the three tables on the right.

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Problem

Apex Systems QA Hub needs a monthly quality metric showing the average number of defects found per tester, broken down by environment, release, and module. Write a PostgreSQL query that calculates this metric from test runs and linked defects.

Requirements

  1. Group results by calendar month, environment, release, and module.
  2. Count defects for each tester within every group, including test runs with zero defects.
  3. Average those tester-level defect totals and return results in chronological order.

Schema

testers
ColumnTypeDescription
tester_idPKINTUnique tester identifier
tester_nameVARCHAR(100)Tester display name
test_runs
ColumnTypeDescription
run_idPKINTUnique test run identifier
tester_idINTTester who executed the run
environmentVARCHAR(40)Execution environment
release_nameVARCHAR(30)Application release under test
moduleVARCHAR(60)Application module tested
executed_atTIMESTAMPTimestamp when the run was executed
defects
ColumnTypeDescription
defect_idPKINTUnique defect identifier
run_idINTTest run that found the defect
severityVARCHAR(20)Defect severity
statusVARCHAR(20)Current defect status
Tablestesterstest_runsdefects
Your solutionPostgreSQL
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