Get the detailed explanation of the ROW_NUMBER() function
row_number() over(partition by field 1 order by field 2) group by partition by field 1 in over, and then sort within the group by order by field 2 in Over, each group starts from 1 here partition by grouping and
group The difference of by is that it can return multiple records in a group, while the aggregation function generally has only one record reflecting the statistical value
Examples are as follows:
Demand scenario (take the latest result information): inspection date, process, work order, specification model, random inspection quantity, defective quantity, random inspection result
Under normal circumstances:
select 检验日期 ，工序，工单，规格型号 ，SUM(抽检数量)，SUM(不良数量)， 抽检结果 from dual
group by
检验日期 ，工序，工单，规格型号 ，抽检结果The result obtained is: each process, work order, and the summed up quantity of specifications and models correspond to multiple inspection results
In the case of using ROW_NUMBER():
-- 取最新一笔的备注信息
WITH NEW_MSG(工序,工单,规格型号,结果 ) AS (
SELECT 工序,工单,规格型号,结果 FROM (
SELECT
工序
,工单
,规格型号
,结果
,row_number() OVER ( PARTITION BY 工序，工单，规格型号 order by 检验日期 desc) AS row
FROM A
)WHERE row=1
)
SELECT
A.检验日期
,A.工序
,A.工单
,A.规格型号
,msg.结果
,sum(抽检数量)
,sum(不良数量)
FROM A.
LEFT JOIN NEW_MSG msg ON msg.工序 = A.工序
AND msg.工单 = A.工单
AND msg.规格型号 = A.规格型号
group by
A.检验日期
,A.工序
,A.工单
,A.规格型号
,msg.结果 The results obtained are: each process, work order, specification and model, corresponding to the latest inspection results