业务场景
需要查询某数据，由于需要三张表关联查询，查询结果如下：

原始SQL语句

SELECT D.ORDER_NUM AS "申请单号" ,D.CREATE_TIME ,D.EMP_NAME AS "申请人",(SELECT extractvalue(t1.row_data,'/root/row/FI13_wasteName')FROM dat_table_row t1WHERE d.document_id = t1.document_idAND t1.table_id     = 'dynamicRowsIdPTFLXX') AS "废料名称",(SELECT extractvalue(t1.row_data,'/root/row/FI13_units')FROM dat_table_row t1WHERE d.document_id = t1.document_idAND t1.table_id     = 'dynamicRowsIdPTFLXX') AS "单位",(SELECT extractvalue(t1.row_data,'/root/row/FI13_estimate')FROM dat_table_row t1WHERE d.document_id = t1.document_idAND t1.table_id     = 'dynamicRowsIdPTFLXX') AS "预估数量",(SELECT extractvalue(t1.row_data,'/root/row/FI13_stockRemoval')FROM dat_table_row t1WHERE d.document_id = t1.document_idAND t1.table_id     = 'dynamicRowsIdPTFLXX') AS "累计出库数量",(SELECT extractvalue(t1.row_data,'/root/row/FI13_receivingTime')FROM dat_table_row t1WHERE d.document_id = t1.document_idAND t1.table_id     = 'dynamicRowsIdCGYTX') AS "收购方收货时间",(SELECT extractvalue(t2.row_data,'/root/row/FI13_collectionTime')FROM dat_table_row t2WHERE d.document_id = t2.document_idAND t2.table_id     = 'dynamicRowsIdPTSJSKSJ') AS "实际收款时间"
FROM dat_document d,dat_table_row dtr
WHERE d.form_name       ='FI14'
AND d.document_id       =dtr.document_id
AND (D.DOCUMENT_STATUS != 'deleted'
OR D.DOCUMENT_STATUS   IS NULL )--AND TO_CHAR(d.create_time,'yyyy-MM-dd') BETWEEN '2020-01-01' AND '2021-03-26'
AND d.order_num = 'FI1420210708002' --FI1420210708002
ORDER BY d.CREATE_TIME DESC;

一、distinct去重

select distinct d.order_num as "申请单号" ,d.create_time ,d.emp_name as "申请人",(select extractvalue(t1.row_data,'/root/row/FI13_wasteName')from dat_table_row t1where d.document_id = t1.document_idand t1.table_id     = 'dynamicRowsIdPTFLXX') as "废料名称",(select extractvalue(t1.row_data,'/root/row/FI13_units')from dat_table_row t1where d.document_id = t1.document_idand t1.table_id     = 'dynamicRowsIdPTFLXX') as "单位",(select extractvalue(t1.row_data,'/root/row/FI13_estimate')from dat_table_row t1where d.document_id = t1.document_idand t1.table_id     = 'dynamicRowsIdPTFLXX') as "预估数量",(select extractvalue(t1.row_data,'/root/row/FI13_stockRemoval')from dat_table_row t1where d.document_id = t1.document_idand t1.table_id     = 'dynamicRowsIdPTFLXX') as "累计出库数量",(select extractvalue(t1.row_data,'/root/row/FI13_receivingTime')from dat_table_row t1where d.document_id = t1.document_idand t1.table_id     = 'dynamicRowsIdCGYTX') as "收购方收货时间",(select extractvalue(t2.row_data,'/root/row/FI13_collectionTime')from dat_table_row t2where d.document_id = t2.document_idand t2.table_id     = 'dynamicRowsIdPTSJSKSJ') as "实际收款时间"
from dat_document d,dat_table_row dtr
where d.form_name       ='FI14'
and d.document_id       =dtr.document_id
and (d.document_status != 'deleted'
or d.document_status   is null )--AND TO_CHAR(d.create_time,'yyyy-MM-dd') BETWEEN '2020-01-01' AND '2021-03-26'
and d.order_num = 'FI1420210708002' --FI1420210708002
order by d.create_time desc;

注意：DISTINCT后面要跟ORDER BY的字段，Oracle先执行 DISTINCT去重后，再使用ORDER BY进行排序的。所以如果在ORDER BY需要排序的字段，没有在 distinct 后的字段中，自然会抛错。
报错信息如下

二、row_number() over()

语法格式

select * from
(select A.*, row_number() over(partition by A.name1 order by A.name12 desc) rn from A)
where rn = 1

select * from (
select d.order_num as "申请单号" ,d.create_time ,d.emp_name as "申请人",(select extractvalue(t1.row_data,'/root/row/FI13_wasteName')from dat_table_row t1where d.document_id = t1.document_idand t1.table_id     = 'dynamicRowsIdPTFLXX') as "废料名称",(select extractvalue(t1.row_data,'/root/row/FI13_units')from dat_table_row t1where d.document_id = t1.document_idand t1.table_id     = 'dynamicRowsIdPTFLXX') as "单位",(select extractvalue(t1.row_data,'/root/row/FI13_estimate')from dat_table_row t1where d.document_id = t1.document_idand t1.table_id     = 'dynamicRowsIdPTFLXX') as "预估数量",(select extractvalue(t1.row_data,'/root/row/FI13_stockRemoval')from dat_table_row t1where d.document_id = t1.document_idand t1.table_id     = 'dynamicRowsIdPTFLXX') as "累计出库数量",(select extractvalue(t1.row_data,'/root/row/FI13_receivingTime')from dat_table_row t1where d.document_id = t1.document_idand t1.table_id     = 'dynamicRowsIdCGYTX') as "收购方收货时间",(select extractvalue(t2.row_data,'/root/row/FI13_collectionTime')from dat_table_row t2where d.document_id = t2.document_idand t2.table_id     = 'dynamicRowsIdPTSJSKSJ') as "实际收款时间",row_number() over(partition by d.order_num  order by d.create_time desc) rn
from dat_document d,dat_table_row dtr
where d.form_name       ='FI14'
and d.document_id       =dtr.document_id
and (d.document_status != 'deleted'
or d.document_status   is null )--AND TO_CHAR(d.create_time,'yyyy-MM-dd') BETWEEN '2020-01-01' AND '2021-03-26'
and d.order_num = 'FI1420210708002' --FI1420210708002
) where rn = 1;

查询结果

参考文章
https://www.cnblogs.com/fina1ly/p/9509795.html
https://blog.csdn.net/deniro_li/article/details/79024099

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Oracle实现去重的两种方式总结

一、distinct去重

二、row_number() over()

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