Trailing whitespace in varchar needs to be considered in comparison

Question

I am using a table with a varchar column. I did not realize that trailing whitespace is not considered in comparisons (and that, apparently, two values that differ only in amount of trailing whitespace will violate the uniqueness property, if specified).

I need to fix this in the table, preferably in place. Is there a recommended path to fixing a table like this in MySQL?

I am accessing the DB strictly through a program I control, so switching to a non-human readable format such as binary would be fine. But I am not sure how to do such a thing and don't want to destroy the table.

Answer 1

I have to assume you're using MySQL 5.x because MySQL 4.x doesn't store trailing spaces in a VARCHAR column.

Using the standard = operator in MySQL, as you indicated, trailing spaces are not considered:

SELECT 'this' = 'this ' returns TRUE

However, LIKE compares the strings character by character, so trailing spaces are significant.

SELECT 'this' LIKE 'this ' returns FALSE.

Both = and LIKE may be case insensitive, using the default collation. Use the COLLATE clause to specify the collation if you need to compare them in a case sensitive manner.