我有这样的数据：
+----+-------------------------+----------+----------+
| ID | DateReceived | Quantity | VendorID |
+----+-------------------------+----------+----------+
| 1 | 2010-08-09 06:53:44.783 | 2 | 1 |
| 2 | 2010-08-01 13:31:26.893 | 1 | 1 |
| 3 | 2010-07-26 07:52:29.403 | 2 | 1 |
| 4 | 2011-03-22 13:31:11.000 | 1 | 2 |
| 5 | 2011-03-22 13:31:11.000 | 1 | 2 |
| 6 | 2011-03-22 11:27:01.000 | 1 | 2 |
| 7 | 2011-03-18 09:04:58.000 | 1 | 1 |
| 8 | 2011-12-17 08:21:29.000 | 1 | 3 |
| 9 | 2012-08-10 10:55:20.000 | 9 | 3 |
| 10 | 2012-08-02 20:18:10.000 | 5 | 1 |
| 11 | 2012-07-12 20:44:36.000 | 3 | 1 |
| 12 | 2012-07-05 20:45:29.000 | 1 | 1 |
| 13 | 2013-03-22 13:31:11.000 | 1 | 2 |
| 14 | 2013-03-22 13:31:11.000 | 1 | 2 |
+----+-------------------------+----------+----------+
我希望按DateReceived对数据进行排序，并将Quantity求和。但是，我希望将Quantity按VendorID分组，只要它们相邻（按DateReceived排序），就像下面的示例输出一样。
+----------+----------+
| VendorID | Quantity |
+----------+----------+
| 1 | 5 |
| 2 | 3 |
| 1 | 1 |
| 3 | 10 |
| 1 | 9 |
| 2 | 2 |
+----------+----------+
我认为答案与变量有关，但我无法思考如何去做。
什么是用于生成所需输出的MySQL查询？
注意：我问了exact same thing here但是对于MS Sql，我现在需要这个用于MySQL。
答案 0 :(得分：0)
select
VendorID,
SUM(Quantity)
from (
select
t.*,
@grn := if(@prev != VendorID, @grn + 1, @grn) as grn,
@prev := VendorID
from
t
, (select @grn := 0, @prev := null) var_init
order by DateReceived
) sq
GROUP BY grn
但是你的预期输出是错误的。你可以通过执行这个来看到这个：
select
t.*,
@grn := if(@prev != VendorID, @grn + 1, @grn) as grn,
@prev := VendorID
from
t
, (select @grn := 0, @prev := null) var_init
order by DateReceived
结果是：
| ID | DATERECEIVED | QUANTITY | VENDORID | GRN | @PREV := VENDORID |
|----|---------------------------------|----------|----------|-----|-------------------|
| 3 | July, 26 2010 07:52:29+0000 | 2 | 1 | 0 | 1 |
| 2 | August, 01 2010 13:31:26+0000 | 1 | 1 | 0 | 1 |
| 1 | August, 09 2010 06:53:44+0000 | 2 | 1 | 0 | 1 |
| 7 | March, 18 2011 09:04:58+0000 | 1 | 1 | 0 | 1 |
| 6 | March, 22 2011 11:27:01+0000 | 1 | 2 | 1 | 2 |
| 4 | March, 22 2011 13:31:11+0000 | 1 | 2 | 1 | 2 |
| 5 | March, 22 2011 13:31:11+0000 | 1 | 2 | 1 | 2 |
| 8 | December, 17 2011 08:21:29+0000 | 1 | 3 | 2 | 3 |
| 12 | July, 05 2012 20:45:29+0000 | 1 | 1 | 3 | 1 |
| 11 | July, 12 2012 20:44:36+0000 | 3 | 1 | 3 | 1 |
| 10 | August, 02 2012 20:18:10+0000 | 5 | 1 | 3 | 1 |
| 9 | August, 10 2012 10:55:20+0000 | 9 | 3 | 4 | 3 |
| 13 | March, 22 2013 13:31:11+0000 | 1 | 2 | 5 | 2 |
| 14 | March, 22 2013 13:31:11+0000 | 1 | 2 | 5 | 2 |
整个查询的结果：
| VENDORID | SUM(QUANTITY) |
|----------|---------------|
| 1 | 6 |
| 2 | 3 |
| 3 | 1 |
| 1 | 9 |
| 3 | 9 |
| 2 | 2 |