SAMPLE_EXPONENTIAL()

All functions > BUSINESS > SAMPLE_EXPONENTIAL()

Returns a value drawn from an exponential distribution with the given rate, based on the given hashing key.

Signatures

Returns: Deterministic value from exponential distribution (>= 0)

SAMPLE_EXPONENTIAL(hashing_key: VARCHAR, rate: DOUBLE) → DOUBLE

Notes

• Deterministic - same key always produces same value
• Uses inverse CDF transform: -ln(HASH01(key)) / rate
• Mean of distribution is 1/rate, variance is 1/rate^2
• Models inter-arrival times in Poisson processes
• Common for queue simulation, time-between-events modeling
• Rate must be strictly positive

Examples

SELECT
    f1 := ROUND(SAMPLE_EXPONENTIAL('k', 0.5E0), 4) -- Exponential draw with rate 0.5 (mean 2.0) for a fixed key
;