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[英]Mysql session variable emulating row_num does not increase in value
[英]How to delete from my query where row_num > 2 in MySql?
我的数据库中有这张表,其架构如下:
nearstops(nearbystopname, latitude, longitude, mainaddress), 我做了如下查询
SELECT
nearbystopname,
latitude,
longitude,
mainaddress,
ROW_NUMBER() OVER (
PARTITION BY
nearbystopname,
mainaddress
ORDER BY
nearbystopname,
mainaddress
) row_num
FROM
DUSAgeocodeDB.nearbystops
这给了我以下信息:
我的问题是,我将如何通过删除 row_num > 2 的结果并将更改反映到我的数据库中来 go ?
我尝试了以下代码:
with cte as (
SELECT
nearbystopname,
latitude,
longitude,
mainaddress,
ROW_NUMBER() OVER (
PARTITION BY
nearbystopname,
mainaddress
ORDER BY
nearbystopname,
mainaddress
) row_num
FROM
DUSAgeocodeDB.nearbystops
) delete from cte where row_num > 1;
但它给了我以下错误:
错误代码:1146。表 'dusageocodedb.cte' 不存在
任何帮助都感激不尽!
假设您在表上有一个主键,那么:
delete ns
from DUSAgeocodeDB.nearbystops ns join
(select nearbystopname, mainaddress, min(id) as min_id
from DUSAgeocodeDB.nearbystops ns2
group by nearbystopname, mainaddress
) ns2
on ns2.nearbystopname = ns.nearbystopname and
ns2.mainaddress = ns.mainaddress and
ns.id > ns.id;
如果您没有主键,最好的办法可能是重新填充表:
create table temp_ns as
select nearbystopname, latitude, longitude, mainaddress,
row_number() over (partition by nearbystopname, mainaddress) as seqnum
from DUSAgeocodeDB.nearbystops ns;
truncate table DUSAgeocodeDB.nearbystops ns; -- SAVE first!!!
insert into DUSAgeocodeDB.nearbystops (nearbystopname, latitude, longitude, mainaddress)
select nearbystopname, latitude, longitude, mainaddress
from temp_ns
where seqnum = 1;
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