MySQL SQLLesson 43Free preview

MySQL Null Functions

This lesson is part of MySQL · All levels

Summary

MySQL provides several functions to handle the NULL values, including IFNULL, COALESCE, and NULLIF. IFNULL replaces the NULL value with a substitute value so that the calculation results or display are more neat. COALESCE is more flexible because it accepts many arguments and returns the first value that is not NULL.

Key points

IFNULL(a, b) returns b when a is NULL, in addition returns a
COALESCE accepted many arguments and returned the first instead of NULL
NULLIF(a, b) yields NULL if a is equal to b, useful to prevent zero division
The value of NULL cannot be compared to = NULL, must use IS NULL
This function is useful so that the report view does not display the word NULL

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