MySql COALESCE function usage code example

COALESCE is a function that refers to each parameter expression in turn (expression_1, expression_2, ..., expression_n), stops when a non-null value is encountered, and returns the value. If all expressions are null, a null value will be returned. The reason for using COALESCE is that most expressions containing NULL values ​​will eventually return NULL.

Application examples:

SELECT COALESCE (1, 2, 3, 4) as number

SELECT COALESCE (NULL, 2, 3, 4) as number

SELECT COALESCE (NULL, NULL, 3, 4) as number

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