Question

这是对优秀答案的后续问题：
SQL Select only rows with Max Value on a Column

SQLFiddle http://sqlfiddle.com/#!2/3077f/2

表“yourtable”：

| id | val | ignore | content |
-------------------------------
| 1  | 10  |   0    |   A     |
| 1  | 20  |   0    |   B     |
| 1  | 30  |   1    |   C     |
| 2  | 40  |   0    |   D     |
| 2  | 50  |   0    |   E     |
| 2  | 60  |   1    |   F     |

在查找每个id的最大值时，使用以下sql：

select yt1.*
from yourtable yt1
left outer join yourtable yt2
on (yt1.id = yt2.id and yt1.val < yt2.val )
where yt2.id is null;

所以结果将是这种情况

| id | val | ignore | content |
-------------------------------
| 1  | 30  |   1    |   C     |
| 2  | 60  |   1    |   F     |

问题当它= 1时，如何按“忽略”列过滤，结果将是

| id | val | ignore | content |
-------------------------------
| 1  | 20  |   0    |   B     |
| 2  | 50  |   0    |   E     |

Answer 1

您需要将条件放在子查询和外部查询中：

select yt1.*
from yourtable yt1 left outer join
     yourtable yt2
     on yt1.id = yt2.id and yt1.val < yt2.val and yt2.ignore <> 1
where yt2.id is null and yt1.ignore <> 1;

Answer 2

您只需添加其他条件and yt1.ignore <> 1，如下所示：

select yt1.*
from yourtable yt1
left outer join yourtable yt2
on (yt1.id = yt2.id and yt1.val < yt2.val )
where yt2.id is null and yt1.ignore <> 1;

SQL仅选择按列过滤的列上具有最大值的行

2 个答案: