MySQL database has a handy and simple string function REPLACE() that allows table data with the matching string (from_string) to be replaced by new string (to_string). This is useful function if you want to search and replace a text string which affects many records or rows, such as change of company name, postcode, URL or spelling mistake.
The syntax of REPLACE is REPLACE(text_string, from_string, to_string)
MySQL reference describes REPLACE as function that returns the string text_string with all occurrences of the string from_string replaced by the string to_string, where matching is case-sensitive when searching for from_string. text_string can be retrieved from the a field in the database table too. Most SQL command can be REPLACE() function, especially SELECT and UPDATE manipulation statement.
update TABLE_NAME set FIELD_NAME = replace(FIELD_NAME, ‘find this string’, ‘replace found string with this string’);
update client_table set company_name = replace(company_name, ‘Old Company’, ‘New Company’)
The above statement will replace all instances of ‘Old Company’ to ‘New Company’ in the field of company_name of client_table table.
Source: MySQL 5.0 Reference Manual