sort by formatted date

[Miguel Rodriguez]

Good morning to everybody.

I encounter a difficulty when formatting a date field by which I order the query with union.

If I make the query with the format that brings the date field (date_time) the result is correct

SELECT fecha, proveedor, importe from db.tb1
UNION
SELECT fecha, proveedor, importe from db2.tb1
order by fecha


but if I format the field with DATE_FORMAT() it orders it by days

SELECT DATE_FORMAT(fecha, "%d-%b") as fecha, proveedor, importe from db.tb1
UNION
SELECT DATE_FORMAT(fecha, "%d-%b") as fecha, proveedor, importe from db2.tb1
order by fecha

How can I correct the order when formatting the dates in different ways?

thank you very much once again for your help