How to Implement Weighted Random Selection in MySQL?

Weighted Random Selection in MySQL

A user seeks to retrieve a random entry from a MySQL table weighted according to the "Multiplier" column. A multiplier of 0 indicates no weighting, while higher values increase the likelihood of selection.

The original query utilizing SELECT and RAND() lacks the ability to implement weighting. To overcome this limitation, an alternative approach has been identified:

ORDER BY -LOG(1.0 - RAND()) / Multiplier

This formula effectively assigns higher random values to entries with higher multipliers. It's important to note that multipliers cannot be set to 0 as it would result in a division by zero error. To exclude entries with a multiplier of 0, a WHERE clause can be applied:

WHERE Multiplier > 0

By combining these elements, the following query achieves weighted random selection:

SELECT *
FROM table
WHERE Multiplier > 0
ORDER BY -LOG(1.0 - RAND()) / Multiplier
LIMIT 1

This formula ensures that entries with higher multipliers have a greater chance of being selected, while maintaining the integrity of the random selection process.

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