UPPER(name)        

➔ Uppercase function.

 SQRT(cost) AS square_root       

➔ Sqrt() gets the square root.

 SELECT AVG(cost) AS average_cost FROM items        

➔ Avg() gets the average.

 SELECT SUM(bids) AS bids FROM items       

➔ Sum() adds all numbers in a column.

 SELECT COUNT(name) FROM items WHERE seller_id = 6       

➔ Counts how many items seller6 is selling.

SELECT COUNT(*) AS item_count,
MAX(cost) AS max
FROM items WHERE seller_id = 12       

➔ How to use multiple aggregate functions, and MAX()/MIN() which return the highest/lowest number, respectively. FUNCTIONS