Google Sheets: How to replace text in column header?

=QUERY(B2:C9;"select (C*100/B)-100 label (C*100/B)-100 'Value'")

https://developers.google.com/chart/interactive/docs/querylanguage#Label

Remember there is a trick there.

Working example of the query:

"SELECT C, COUNT(C), AVG(G), AVG(E) GROUP BY C ORDER BY COUNT(C) DESC LABEL COUNT(C) 'My count' FORMAT AVG(G) '##0.00', AVG(E) '##0.00'"

Not working example of the query:

"SELECT C, COUNT(C) LABEL COUNT(C) 'My count', AVG(G), AVG(E) GROUP BY C ORDER BY COUNT(C) DESC FORMAT AVG(G) '##0.00', AVG(E) '##0.00'"

Also not working example of the query:

"SELECT C, COUNT(C), AVG(G), AVG(E) GROUP BY C ORDER BY COUNT(C) DESC FORMAT AVG(G) '##0.00', AVG(E) '##0.00' LABEL COUNT(C) 'My count'"

It works ONLY if it's placed in the correct order with other commands.