STDDEV_SAMP

1
SELECT
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  department,
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  COUNT(*) as sample_size,
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  ROUND(STDDEV_SAMP(salary), 2) as salary_stddev
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FROM employee_survey
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GROUP BY department;

1
SELECT
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  batch_id,
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  AVG(weight) as avg_weight,
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  STDDEV_SAMP(weight) as weight_stddev,
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  CASE
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    WHEN STDDEV_SAMP(weight) > 5 THEN 'HIGH_VARIANCE'
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    WHEN STDDEV_SAMP(weight) > 2 THEN 'MODERATE'
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    ELSE 'LOW_VARIANCE'
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  END as quality_flag
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FROM production_samples
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GROUP BY batch_id;