replace 0 with null in mysql

Question

I want to replace 0's in mysql table with 'NULL'. I have read that querying the following way would replace 'NULL' with 0

SELECT COALESCE(null_column, 0) AS null_column FROM whatever;

But how to the other way?

Answer 1

You can use NULLIF, which will return NULL if the value in the first parameter matches the value in the second parameter.

SELECT NULLIF(null_column, 0) AS null_column FROM whatever

Answer 2

update `whatever` set `null_column` = null where null_column = 0;