How to remove leading and trailing whitespace in a MySQL field?

You're looking for TRIM.

UPDATE FOO set FIELD2 = TRIM(FIELD2);

Seems like it might be worth it to mention that TRIM can support multiple types of whitespace, but only one at a time and it will use a space by default. You can, however, nest TRIMs.

 TRIM(BOTH ' ' FROM TRIM(BOTH '\n' FROM column))

If you really want to get rid of all the whitespace in one call, you're better off using REGEXP_REPLACE along with the [[:space:]] notation. Here is an example:

SELECT 
    -- using concat to show that the whitespace is actually removed.
    CONCAT(
         '+', 
         REGEXP_REPLACE(
             '    ha ppy    ', 
             -- This regexp matches 1 or more spaces at the beginning with ^[[:space:]]+
             -- And 1 or more spaces at the end with [[:space:]]+$
             -- By grouping them with `()` and splitting them with the `|`
             -- we match all of the expected values.
             '(^[[:space:]]+|[[:space:]]+$)', 

             -- Replace the above with nothing
             ''
         ), 
         '+') 
    as my_example;
-- outputs +ha ppy+

A general answer that I composed from your answers and from other links and it worked for me and I wrote it in a comment is:

 UPDATE FOO set FIELD2 = TRIM(Replace(Replace(Replace(FIELD2,'\t',''),'\n',''),'\r',''));

etc.

Because trim() doesn't remove all the white spaces so it's better to replace all the white spaces u want and than trim it.

Hope I could help you with sharing my answer :)

Just to be clear, TRIM by default only remove spaces (not all whitespaces). Here is the doc: http://dev.mysql.com/doc/refman/5.0/en/string-functions.html#function_trim

Please understand the use case before using this solution:

trim does not work while doing select query

This works

select replace(name , ' ','') from test;

While this doesn't

select trim(name) from test;