mysql: how to truncate the length of a field

Question

Alter table merry_parents change mobile mobile char(10).

When I do the above I'm getting error:

#1265 - Data truncated for column 'mobile' at row 2

How can I truncate my mobile field to char(10)? Currently it is char(12).

Answer 1

The error is telling you that there is data 12 characters long in row 2 (and probably others) so it's stopped the alter command to avoid losing data.

Try updating your table using SUBSTRING() to shorten the column. It's unclear why you want to do this as you'll lose data, but this will truncate the data to 10 characters long:

UPDATE merry_parents SET mobile=SUBSTRING(mobile, 1, 10)

Then run your alter command:

ALTER TABLE merry_parents CHANGE mobile mobile char(10).