MYSQL根据JOIN中的ID选择最新结果，以防止重复

Question

这是我现在的查询

SELECT
list.WorkOrder,
list.Address,
list.Subdivision,
list.Section,
locateparsed.LocateParsedID,
locateparsed.WorkDate
FROM list
LEFT JOIN locateparsed ON locateparsed.WorkOrder = list.WorkOrder
WHERE list.Completed = 0
AND locateparsed.WorkDate IS NOT NULL

输出类似于

WorkOrder | Address   | Subdivision | Section | LocateParsedID | WorkDate
12345678  | 123 test  | test        | sec 1   |             75 | 01/01/0101
12345678  | 123 test  | test        | sec 1   |             10 | 01/01/0101
12345680  | 1233 test | test        | sec 1   |             55 | 01/01/0101
12345644  | 1234 test | test        | sec 1   |             96 | 01/01/0101
12345555  | 1235 test | test        | sec 1   |             35 | 01/01/0101

我希望自75以来的输出高于10

WorkOrder | Address  | Subdivision | Section | LocateParsedID | WorkDate
12345678 | 123 test  | test        | sec 1   |             75 | 01/01/0101
12345680 | 1233 test | test        | sec 1   |             55 | 01/01/0101
12345644 | 1234 test | test        | sec 1   |             96 | 01/01/0101
12345555 | 1235 test | test        | sec 1   |             35 | 01/01/0101

Answer 1

您可以使用每个Section包含最大WorkOrder值的派生表。您可以加入此表以过滤重复项：

SELECT l1.WorkOrder,
       l1.Address,
       l1.Subdivision,
       l1.Section,
       lp.LocateParsedID,
       lp.WorkDate
FROM list AS l1
INNER JOIN (
   SELECT WorkOrder, MAX(Section) AS Section
   FROM list
   GROUP BY WorkOrder
) AS l2 ON l1.WorkOrder = l2.WorkOrder AND l1.Section = l2.Section
INNER JOIN locateparsed AS lp
   ON lp.WorkOrder = l2.WorkOrder
WHERE l1.Completed = 0 AND lp.WorkDate IS NOT NULL

注意： LEFT JOIN基本上是INNER JOIN，因为WorkDate IS NOT NULL条款中的WHERE而不是ON }。clause。