[英]Query select rows based on distinct values of a column
我当前的查询有问题,我希望根据列获取记录/结果(示例列 Status 的值为 new/pending/completed 对于我执行的查询,如果有 3 个状态为 new 的记录,它应该是过滤以仅显示 1 条状态为新的记录)。 下面是我当前的查询,它得到重复的列。
select a.CW_UPD_TMS,
case when a.CW_CRT_UID='AAA' then 'BBB'
else a.CW_CRT_UID end as CW_CRT_UID,
COALESCE(b.CW_S_BR, a.CW_S_BR) as CW_S_BR,
a.CW_TRX_STAT as STATUS,
SUBSTR(a.CW_UPD_TMS,7,2) as day,
SUBSTR(a.CW_UPD_TMS,5,2) as month,
SUBSTR(a.CW_UPD_TMS,1,4) as ayear,
SUBSTR(a.CW_UPD_TMS,9,2) as hours,
SUBSTR(a.CW_UPD_TMS,11,2) as mins,
SUBSTR(a.CW_UPD_TMS,13,2) as secs,
case when cast(SUBSTR(a.CW_UPD_TMS,9,2) as INT) > 12 then 'PM'
else 'AM' end as zone
from TABLEA a
left outer join TABLEB b on a.CW_CRT_UID = b.CW_S_USR
where a.CW_TRX_ID = '20150415110000798'
union
select a.CW_UPD_TMS,
case when a.CW_CRT_UID='AAA' then 'BBB'
else a.CW_CRT_UID end as CW_CRT_UID,
COALESCE(b.CW_S_BR, a.CW_S_BR) as CW_S_BR,
a.CW_TRX_STAT as STATUS,
SUBSTR(a.CW_UPD_TMS,7,2) as day,
SUBSTR(a.CW_UPD_TMS,5,2) as month,
SUBSTR(a.CW_UPD_TMS,1,4) as ayear,
SUBSTR(a.CW_UPD_TMS,9,2) as hours,
SUBSTR(a.CW_UPD_TMS,11,2) as mins,
SUBSTR(a.CW_UPD_TMS,13,2) as secs,
case when cast(SUBSTR(a.CW_UPD_TMS,9,2) as INT) > 12 then 'PM'
else 'AM' end as zone
from TABLEC a
left outer join TABLEB b on a.CW_CRT_UID = b.CW_S_USR
where a.CW_TRX_ID = '20150415110000798'
这是当前的结果:
CW_UPD_TMS CW_CRT_UID CW_S_BR STATUS DAY MONTH AYEAR HOURS MINS SECS ZONE
2015062610260746811 happy KLC NEW 26 06 2015 10 26 07 AM
2015062610273984711 happy KLC NEW 26 06 2015 10 27 39 AM
2015062610275762511 happy KLC NEW 26 06 2015 10 27 57 AM
那么现在如何更改查询,以便仅显示 1 条记录(显示 min(CW_UPD_TMS)),因为现在 3 条记录具有相同的 STATUS (New) 。
我的预期结果应该是:
CW_UPD_TMS CW_CRT_UID CW_S_BR STATUS DAY MONTH AYEAR HOURS MINS SECS ZONE
2015062610260746811 happy KLC NEW 26 06 2015 10 26 07 AM
对不起我糟糕的英语。
它在您的情况下的预期行为。 除了“状态”之外,您还应该想出另一列,以便它们可以形成复合键,这将是唯一的,并且您可以获得单个记录。
您可以有任何标准,如日期或任何符合您要求的标准,并使用行号属性来限制结果为 1 条记录。
让我知道这是否有意义。
这可能是一个好的开始,但我不得不假设时间戳作为主键。 您应该在问题中提及您在哪个平台上。 如果我们了解 join 和 union 发生了什么,它也可能会更清晰。
select
d.CW_UPD_TMS, CW_CRT_UID, CW_S_BR, STATUS, day, month, ayear, hours, mins, secs, zone
from
(
select
a.CW_UPD_TMS, case when a.CW_CRT_UID='AAA' then 'BBB' else a.CW_CRT_UID end as CW_CRT_UID,
case when b.CW_S_BR is null then a.CW_S_BR else b.CW_S_BR end as CW_S_BR, a.CW_TRX_STAT as STATUS,
SUBSTR(a.CW_UPD_TMS,7,2) as day, SUBSTR(a.CW_UPD_TMS,5,2) as month, SUBSTR(a.CW_UPD_TMS,1,4) as ayear,
SUBSTR(a.CW_UPD_TMS,9,2) as hours, SUBSTR(a.CW_UPD_TMS,11,2) as mins,SUBSTR(a.CW_UPD_TMS,13,2) as secs,
case when cast(SUBSTR(a.CW_UPD_TMS,9,2) as INT) > 12 then 'PM' else 'AM' end as zone
from TABLEA a left outer join TABLEB b on a.CW_CRT_UID = b.CW_S_USR
where a.CW_TRX_ID = '20150415110000798'
union
select
a.CW_UPD_TMS, case when a.CW_CRT_UID='AAA' then 'BBB' else a.CW_CRT_UID end as CW_CRT_UID,
case when b.CW_S_BR is null then a.CW_S_BR else b.CW_S_BR end as CW_S_BR, a.CW_TRX_STAT as STATUS,
SUBSTR(a.CW_UPD_TMS,7,2) as day, SUBSTR(a.CW_UPD_TMS,5,2) as month, SUBSTR(a.CW_UPD_TMS,1,4) as ayear,
SUBSTR(a.CW_UPD_TMS,9,2) as hours, SUBSTR(a.CW_UPD_TMS,11,2) as mins,SUBSTR(a.CW_UPD_TMS,13,2) as secs,
case when cast(SUBSTR(a.CW_UPD_TMS,9,2) as INT) > 12 then 'PM' else 'AM' end as zone
from TABLEC a
left outer join TABLEB b on a.CW_CRT_UID = b.CW_S_USR
where a.CW_TRX_ID = '20150415110000798'
) as d /* data */ inner join
(
select min(CW_UPD_TMS) as CW_UPD_TMS, CW_TRX_STAT
from (
select a.CW_UPD_TMS, a.CW_TRX_STAT
from TABLEA a
where a.CW_TRX_ID = '20150415110000798'
union
select c.CW_UPD_TMS, c.CW_TRX_STAT
from TABLEC c
where c.CW_TRX_ID = '20150415110000798'
) t0
group by CW_TRX_STAT
) as r /* representative */
on r.CW_UPD_TMS = d.CW_UPD_TMS and r.CW_TRX_STAT = d.CW_TRX_STAT
要获取最旧的记录,您需要按日期对记录进行排名。 因此,您要做的是将 TableA 和 TableC 结合起来,给记录一个数字,每个状态中最旧的为 1,然后只保留这些记录排名 1。
select a.cw_upd_tms,
case when a.cw_crt_uid='AAA' then 'BBB'
else a.cw_crt_uid end as cw_crt_uid,
coalesce(b.cw_s_br, a.cw_s_br) as cw_s_br,
a.cw_trx_stat as status,
substr(a.cw_upd_tms,7,2) as day,
substr(a.cw_upd_tms,5,2) as month,
substr(a.cw_upd_tms,1,4) as ayear,
substr(a.cw_upd_tms,9,2) as hours,
substr(a.cw_upd_tms,11,2) as mins,
substr(a.cw_upd_tms,13,2) as secs,
case when cast(substr(a.cw_upd_tms,9,2) as int) > 12 then 'PM'
else 'AM' end as zone
from
(
select
cw_trx_stat, cw_crt_uid, cw_upd_tms
from
(
select
cw_trx_stat, cw_crt_uid, cw_upd_tms,
row_number() over (partition by cw_trx_stat order by cw_upd_tms) as rn
from
(
select cw_trx_stat, cw_crt_uid, cw_upd_tms
from tablea where cw_trx_id = '20150415110000798'
union all
select cw_trx_stat, cw_crt_uid, cw_upd_tms
from tablec where cw_trx_id = '20150415110000798'
) combined
) ranked
where rn = 1
) a
left outer join tableb b on a.cw_crt_uid = b.cw_s_usr;
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