Question

我有一个查询，它会累计订单的总价值（每种产品的数量*价格总和）。我想要一个包含仅＃＆＃34; A＆＃34;的总值的列。大小的产品。所以它应该总结所有产品的数量*价格，除了＆＃34; C＆＃34;尺寸产品。

只要我为每个产品返回一行，我就会得到预期的结果：每个A尺寸产品为5美元，C尺寸产品为0美元（在smallsize列中）。

SELECT
part_num, email, b.item, b.size_code,
IF(b.size_code IN ('A','B'), quan * price,0) AS smallsize,
quan * price AS price
FROM `orders` AS b
INNER JOIN `groups` AS a
  ON b.ordnum = a.line_num
INNER JOIN `prices` AS c
  ON c.item = b.item AND c.size_code = b.size_code

| part_num |        email | item | size_code | smallsize | price |
|----------|--------------|------|-----------|-----------|-------|
|        2 | me@email.com | 7400 |         A |         5 |     5 |
|        2 | me@email.com | 7400 |         C |         0 |    20 |
|        2 | me@email.com | 7790 |         A |         5 |     5 |
|        2 | me@email.com | 7870 |         A |         5 |     5 |
|        2 | me@email.com | 7910 |         A |         5 |     5 |

但是当我试图总结价格时，C尺寸产品包含在总数中（$ 5 + $ 5 + $ 5 + $ 5 + $ 20 = $ 40）。

SELECT
part_num, email,
IF(b.size_code IN ('A','B'), sum(quan * price),0) AS smallsize,
sum(quan * price) AS price
FROM `orders` AS b
INNER JOIN `groups` AS a
  ON b.ordnum = a.line_num
INNER JOIN `prices` AS c
  ON c.item = b.item AND c.size_code = b.size_code;

| part_num |        email | smallsize | price |
|----------|--------------|-----------|-------|
|        2 | me@email.com |        40 |    40 |

为什么第一个查询总共返回$ 20（如果你将smallsize列加起来），第二个查询返回$ 40为smallsize？

我创建了一个sqlfiddle来说明：http://sqlfiddle.com/#!9/b5ccd8/4

Answer 1

您应该将IF表达式放在SUM内。否则你总结所有行，然后IF决定是否在最终结果中显示总和或0（这是不确定的，取决于它恰好选择哪一行b.size。

SELECT
part_num, email,
    sum(IF(b.size_code IN ('A','B'), quan * price,0)) AS smallsize,
    sum(quan * price) AS price
FROM `orders` AS b
INNER JOIN `groups` AS a
  ON b.ordnum = a.line_num
INNER JOIN `prices` AS c
  ON c.item = b.item AND c.size_code = b.size_code;

DEMO

使用条件，我得到的结果会有所不同，具体取决于我是否使用SUM

1 个答案: