Select average from MySQL table with LIMIT

问题

I am trying to get the average of the lowest 5 priced items, grouped by the username attached to them. However, the below query gives the average price for each user (which of course is the price), but I just want one answer returned.

SELECT AVG(price) 
  FROM table 
 WHERE price > '0' && item_id = '$id' 
GROUP BY username 
ORDER BY price ASC 
   LIMIT 5

回答1:

I think this is what you're after:

SELECT AVG(items.price)
  FROM (SELECT t.price
          FROM TABLE t
         WHERE t.price > '0' 
           AND t.item_id = '$id'
      ORDER BY t.price
         LIMIT 5) items

It will return the average of the 5 lowest prices - a single answer.

回答2:

Simple solution below.

Query:

SELECT  AVG(Column_name) 
FROM  (SELECT Column_name 
FROM  Table
WHERE  ColumnID < number[Limit you want] )

来源：https://stackoverflow.com/questions/1854383/select-average-from-mysql-table-with-limit