Can you tell me specifically which database you are using, such as Oracle or MySQL? if you are using pgsql
SELECT
sf.StaffName,
TO_CHAR(st.SalesDate, 'DD Mon YYYY') AS SalesDateFormatted,
fi.ItemName,
CONCAT('$', TO_CHAR(SUM(fi.ItemSalesPrice * st.Quantity), 'FM9999990.00')) AS TotalPrice
FROM SalesTransaction st
JOIN Staff sf ON st.StaffID = sf.StaffID
JOIN SalesTransactionDetail sd ON st.SalesTransactionID = sd.SalesTransactionID
JOIN FashionItems fi ON sd.ItemID = fi.ItemID
WHERE LENGTH(sf.StaffName) > (SELECT AVG(LENGTH(StaffName)) FROM Staff)
AND EXTRACT(DAY FROM st.SalesDate) % 2 != 0
GROUP BY sf.StaffName, st.SalesDate, fi.ItemName;
can you try this sql?