You can use the SELECT statement with the INTO and OUTFILE clauses.
See: http://dev.mysql.com/doc/refman/5.7/en/select-into.html
SELECT html
FROM mytable
WHERE lang = 'fr'
INTO OUTFILE 'frdata.txt'
The following SQL query might be used to generate one file output statement per row in the table. Note the use of the CONCAT function to build a new SQL SELECT INTO OUTFILE command per row.
SELECT CONCAT( 'SELECT html from mytable where lang=''', lang, '''', ' INTO OUTFILE ''', CAST(id AS CHAR), '_', lang, '.html'';')
FROM mytable
ORDER BY id;
This will yield the the statements:
SELECT html from mytable where lang='fr' INTO OUTFILE '20_fr.html';
SELECT html from mytable where lang='de' INTO OUTFILE '21_de.html';
SELECT html from mytable where lang='it' INTO OUTFILE '22_it.html';
...