Veja como verificar quais colunas são o agrupamento errado:
SELECT table_schema, table_name, column_name, character_set_name, collation_name
FROM information_schema.columns
WHERE collation_name = 'latin1_general_ci'
ORDER BY table_schema, table_name,ordinal_position;
E aqui está a consulta para corrigi-lo:
ALTER TABLE tbl_name CONVERT TO CHARACTER SET latin1 COLLATE 'latin1_swedish_ci';
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