view binary data as text

SELECT DISTINCT d1.id_master,group_concat(d1.id_master),d.term,d.id_tezaver,d.Auto_taxonomy_check_fail,g.id_tezaver AS galery_id_tezaver,t.id_tezaver_obfuscated, GROUP_CONCAT(DISTINCT g.id_galery_obfuscated) AS id_galery_obfuscated, GROUP_CONCAT(DISTINCT tt1.term) AS taxa
FROM tezaver_zunanji_spiski_detail d
LEFT JOIN tezaver_taxonomy tt1 ON d.id_tezaver = tt1.id_tezaver
LEFT JOIN galery_1 g ON d.id_tezaver = g.id_tezaver
LEFT JOIN tezaver t ON t.id_tezaver = d.id_tezaver
left join tezaver_zunanji_spiski_detail d1 on d.term = d1.term
WHERE d.id_master = 100 AND LOCATE(' ', d.term) <> 0
GROUP BY d.term
ORDER BY d.term

pay attention to:

d1.id_master,group_concat(d1.id_master)

result: 
100 | 0x313030

upon clicking

view binary data as text

100 | 100

id_master is type of int

I think GROUP_CONCAT is turning many column types to binary.

HeidiSQL does not examine the content to determine the data type, but the meta information shipped with mysql_fetch_field_direct(). Watch out for "enum_field_types type" on the bottom of the documentation page.