Illegal mix of collations (utf8_unicode_ci,IMPLICIT) and (utf8_general_ci,IMPLICIT) for operation '='

Question

Error message on MySql:

Illegal mix of collations (utf8_unicode_ci,IMPLICIT) and (utf8_general_ci,IMPLICIT) for operation \'=\'

I have gone

Answer 1

I had a similar problem, but it occurred to me inside procedure, when my query param was set using variable e.g. SET @value='foo'.

What was causing this was mismatched collation_connection and Database collation. Changed collation_connection to match collation_database and problem went away. I think this is more elegant approach than adding COLLATE after param/value.

To sum up: all collations must match. Use SHOW VARIABLES and make sure collation_connection and collation_database match (also check table collation using SHOW TABLE STATUS [table_name]).