How Can I Prevent NULL Values from Ruining My MySQL CONCAT Results?

NULL Values Distorting CONCAT Function in MySQL

Executing a CONCAT query on a table containing NULL values can lead to unexpected results. In the example provided, the NULL values in certain fields are causing the entire CONCAT result to become NULL.

To address this, the COALESCE function can be used to handle NULL values gracefully. COALESCE accepts two arguments: the field being evaluated, and the value to substitute if the field is NULL. By wrapping each potentially NULL field in COALESCE, we can replace NULL values with an empty string ('').

The modified query with COALESCE applied:

SELECT CONCAT(COALESCE(`affiliate_name`,''),'-',COALESCE(`model`,''),'-',COALESCE(`ip`,''),'-',COALESCE(`os_type`,''),'-',COALESCE(`os_version`,'')) AS device_name
FROM devices

This query will now return the desired result, ignoring NULL values and concatenating non-NULL values into a single string:

cs1-Dell-10.125.103.25-Linux-Fedora
cs2-Dell-10.125.103.26-Linux-Fedora
cs3-Dell-10.125.103.27-
cs4-Dell-10.125.103.28-

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