Why CONCAT with aggregation functions returns the BLOB?

Good time of day. Solve the problem using aggregate functions:

5e94357feacae055448610.png
But when trying to connect the string via CONCAT returns BLOB value. When I use aggregate functions without the concatenation, the result is output stable. I made a mistake, and how to connect them?
Query:
SELECT
CASE
WHEN DAYOFWEEK(BIRTHDAY) = 1 THEN 'Sunday'
WHEN DAYOFWEEK(BIRTHDAY) = 2 THEN 'Monday'
WHEN DAYOFWEEK(BIRTHDAY) = 3 THEN 'Tuesday'
WHEN DAYOFWEEK(BIRTHDAY) = 4 THEN 'Wednesday'
WHEN DAYOFWEEK(BIRTHDAY) = 5 THEN 'Thursday'
WHEN DAYOFWEEK(BIRTHDAY) = 6 THEN 'Friday'
WHEN DAYOFWEEK(BIRTHDAY) = 8 THEN 'Saturday'
ELSE 'a person's Age is not specified'
END 'IN the <day of week>', CONCAT(COUNT(*), 'test'), AVG(VES), MIN(ROST) FROM stud WHERE VES < VES 55 OR > 80 GROUP BY DAYOFWEEK(BIRTHDAY);

Conclusion:
5e9436929ac56754115599.png
April 18th 20 at 13:31
1 answer
April 18th 20 at 13:33
Solution
Make CAST
Thank you - frederique_Batz84 commented on April 18th 20 at 13:36

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