[英]Return one row from a left outer join
我有以下工作正常:
SELECT mcr.mat_change_req_id, mcr.line_item_number
, r.remarks, r.remarks_date
FROM mat_change_req mcr
left outer join mat_change_req_remarks r ON mcr.mat_change_req_id = r.mat_change_req_id
WHERE mcr.contract_id = 'IR-30910'
AND
mcr.project_number = '0801082'
問題是表mat_change_req_remarks(r)與mat_change_req(mcr)有多對一的關系,因此,如果r有多行,則上面的查詢將為r中的每一個倍數返回一行。
我只想返回MIN(r.remarks_date)的倍數,則從r返回一行。 r.remarks_date是日期字段。
提前致謝!
像這樣:
SELECT mcr.mat_change_req_id,
mcr.line_item_number,
r.remarks,
r.remarks_date
FROM mat_change_req mcr
left outer join (
select mat_change_req_id,
remarks,
remarks_date,
row_number() over (partition by mat_change_req_id order by remarks_date) as rn
from mat_change_req_remarks
) r ON mcr.mat_change_req_id = r.mat_change_req_id and r.rn = 1
WHERE mcr.contract_id = 'IR-30910'
AND mcr.project_number = '0801082'
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