MySQL alter table modify column failing at rows with null values

Question

I have a table with about 10K rows, which I am trying to alter so that the field fielddelimiter is never null. I am attempting to do an alter statement, expecting a

Answer 1

In my case I was setting the column to NOT NULL

ALTER TABLE `request_info` 
CHANGE COLUMN `col_2` `col_2` 
VARCHAR(2000) 
NOT NULL -- here was setting it to NULL when the existing col allowed NULL
AFTER `col_1`

when previously I set the column to DEFAULT NULL (i.e. allow NULL values), so if you want to allow NULL then you can do the following:

ALTER TABLE `request_info` 
CHANGE COLUMN `col_2` `col_2` 
VARCHAR(2000) 
DEFAULT NULL -- changed from NOT --> DEFAULT 
AFTER `col_1`