Why group by (mysql) does not work?

Why group by (mysql) does not work? After all, it should leave only one field continent, and all others to remove that again? Don't quite understand how it works

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June 26th 19 at 14:08
2 answers
June 26th 19 at 14:10
The sample must be either a field in GROUP BY or aggregate functions (SUM, AVG, COUNT, etc.)
Well, certainly not *
June 26th 19 at 14:12
Or set the mode sql_mode=only_full_group_by

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