mysql - How to fix double-encoded UTF8 characters (in an utf-8 table)

Question

A previous LOAD DATA INFILE was run under the assumption that the CSV file is latin1-encoded. During this import the multibyte characters were interpreted as two single character and then encoded using utf-8 (again).

This double-encoding created anomalies like ???± instead of ?.

How to correct these strings?

Answer 1

The following MySQL function will return the correct utf8 string after double-encoding:

CONVERT(CAST(CONVERT(field USING latin1) AS BINARY) USING utf8)

It can be used with an UPDATE statement to correct the fields:

UPDATE tablename SET
    field = CONVERT(CAST(CONVERT(field USING latin1) AS BINARY) USING utf8);