The error message looked like:
“Illegal mix of collations (latin1_swedish_ci,COERCIBLE) and (utf8_general_ci,IMPLICIT) for operation ‘find_in_set’”

I ran into this problem today while importing text from a CSV file. Evidently, the text format of the document had UTF characters, which caused CodeIgniter to error out when it tried to insert it to the database. The line had French characters (The ç in Français) My database fields by default are set to “latin1_swedish_ci” character set.

The fix?
I decided the best way to fix this was to set the Collation option for that specific field in the MySQL database to  “utf8_general_ci” from “latin1_bin”. Re-import the data back into the database and it should preserve the character set. Its a good idea to set text fields to UTF-8, especially if you anticipate getting UTF characters.