LOG10

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SELECT
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  value,
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  LOG10(value) as log10_val,
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  FLOOR(LOG10(value)) as magnitude
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FROM (
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  SELECT unnest([5, 50, 500, 5000, 50000]) as value
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);

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SELECT
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  CASE FLOOR(LOG10(amount))
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    WHEN 3 THEN 'Thousands'
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    WHEN 4 THEN 'Ten Thousands'
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    WHEN 5 THEN 'Hundred Thousands'
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    WHEN 6 THEN 'Millions'
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    ELSE 'Other'
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  END as amount_range,
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  COUNT(*) as transaction_count
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FROM transactions
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GROUP BY FLOOR(LOG10(amount));

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SELECT
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  signal_power,
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  reference_power,
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  10 * LOG10(signal_power / reference_power) as decibels
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FROM signal_measurements;