MySQL如何将WHERE子句应用于除一个以外的所有选定列？

Question

I am totalling columns and grouping them by a column "fruits" like this: (based on my previous question on SO )

SELECT `fruits`, sum(amount), sum(price)
FROM `accounts` 
GROUP BY fruits

I have now added a date column to the table and i'm trying to filter the result by dates like this:

SELECT `fruits`, sum(amount), sum(price)
FROM `accounts` 
WHERE `userid` = 1 AND `date` BETWEEN "2010-11-01" AND "2015-12-22"
GROUP BY fruits

This works fine and I get the filtered results. However, if a fruit has not been entered between the two dates, it naturally doesn't show up because the WHERE clause also includes the fruits .

So, my question is how can I write a query where it gets all the fruits regardless of the dates but filters only the amount and price column by dates?

Answer 1

Theres' a couple of approaches. One is to use conditional aggregation. Remove the predicate, and move the conditional test to an expression in the SELECT list. For example, something like this:

SELECT a.fruits
     , SUM( IF(a.userid = 1 AND a.date BETWEEN '2010-11-01' AND '2015-12-22'
              ,a.amount,0)
       ) AS `tot_amount`
     , SUM( IF(a.userid = 1 AND a.date BETWEEN '2010-11-01' AND '2015-12-22'
              ,a.price,0)
       ) AS `tot_price`
  FROM `accounts` a
 GROUP BY a.fruits

Other approaches will use a row source that returns the values of fruits you want returned, and then an "outer join" to the totals from your original query. Or for a reasonably small number of rows, you could use correlated subqueries in the SELECT list.

Let's say that this returns the set of fruits you want to returned:

SELECT s.fruits
  FROM `accounts` s
 GROUP BY s.fruits

We can wrap that in parens, and use it as a rowsource like it was a table. As a trivial example of that:

SELECT f.fruits
  FROM ( 
         SELECT s.fruits
           FROM `accounts` s
          GROUP BY s.fruits
       ) f

Now we could do the same thing with your original query, wrap it in parens and make it an inline view:

SELECT f.fruits
     , IFNULL(t.tot_amount,0) AS tot_amount
     , IFNULL(t.tot_price,0)  AS tot_price
  FROM ( 
         SELECT s.fruits
           FROM `accounts` s
          GROUP BY s.fruits
       ) f
  LEFT
  JOIN (  
         -- original query here 
         SELECT a.`fruits`
              , sum(a.amount) AS tot_amount
              , sum(a.price) AS tot_price
           FROM `accounts` a
          WHERE a.`userid` = 1
            AND a.`date` BETWEEN '2010-11-01' AND '2015-12-22'
          GROUP BY a.fruits
       ) t
    ON t.fruits = f.fruits

Answer 2

You can do it using a left join:

SELECT t.`fruits`,sum(coalesce(s.amount,0)),sum(coalesce(s.price,0))
FROM(SELECT DISTINCT `fruits` FROM `accouts`) t
LEFT OUTER JOIN `accounts` s
 ON(t.`fruits` = s.`fruits` AND s.`userid` = 1
    AND s.`date` BETWEEN "2010-11-01" AND "2015-12-22")
GROUP BY t.`fruits`

Answer 3

Try this:

SELECT 
    `fruits`, 
    sum((`date` BETWEEN "2010-11-01" AND "2015-12-22") * amount) total_amount,
    sum((`date` BETWEEN "2010-11-01" AND "2015-12-22") * price) total_price
FROM `accounts` 
WHERE `userid` = 1
GROUP BY fruits

Answer 4

you can do by this one:

SELECT a1.`fruits`, sum(a1.amount), sum(a1.price)
FROM `accounts` a1
LEFT OUTER JOIN `accounts` a2 ON a1.fruits = a2.fruits 
AND a2.`userid` = 1 AND a2.`date` BETWEEN "2010-11-01" AND "2015-12-22" 
GROUP BY a1.fruits