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  • PostgreSQL:如何使用ORDER BY DISTINCT ON?(2 个回答)

    我想运行以下查询: select distinct on (address_id) purchases.address_id,purchases.*from purchaseswhere purchases.product_id = 1order bypurchases.purchased_at desc 但我知道这个错误: pg::error: error:select distinct on expressions must match initial order by expressions...
  • Postgres DISTINCT与DISTINCT ON有什么不同?(2 个回答)

    第一个命令比第二个命令返回更多结果 -- command 1select distinctcount(dimension1)from data_table; -- command 2 select count(*)from (select distinct on (dimension1)dimension1from data_tablegroup by dimension1) as tmp_table; 以下查询都返回1504 select count(*)from data_table where dimension1 is not...
  • DISTINCT ON在postgres中的聚合函数中如何使用?(2 个回答)

    相反,我想要一个只有郊区和城市的数组,像这样:我可以json_agg(distinct tag.name),但是这只会产生一个标签名称数组,当我想整个行作为json。 我想json_agg(distinct on(tag.name) tag.*),但这显然不是有效的sql。 那么我怎样才能distinct on在postgres的一个聚合函数里模拟呢?...
  • SELECT

    distinct 子句如果指定了 distinct 子句,所有重复的行会被从结果集中移除(为每一组重复的行保留一行)。 all 则指定相反的行为,所有行都会被保留,这也是默认情况。 distinct on ( expression ) 只保留在给定表达式上计算相等的行集合中的第一行。 distinct on 表达式使用和 order by 相同的规则(见上文)解释...
  • 在Django中使用DISTINCT

    when you specify field names, youmustprovide anorder_by()in thequeryset,and the fields inorder_by()must start with the fields indistinct(),in the same order.for example,selectdistincton(a)gives you the first row for each value in columna. if youdon’t specify an order, you’ll get some ...
  • postgresql中使用distinct去重

    造成这种需求的原因是单表设计不合理,没有拆分成多表,造成多字段冗余,除了唯一性标志外,其他字段是相同的。 目标是,取出其他字段,忽略唯一标志。 因为其他字段有重复,需要去掉重复。 # select distinct on (code) code,id, namefrom test_dist; code | id | name-----+----+----- 1 | 1 | a 2 | 4 | m 3 | 6 ...
  • 一个问题:CDS view在HANA studio里执行,显示的耗时比在ABAP open SQL里少

    from: wang, jerrysent: monday, july 17, 2017 7:38 amhi sungheun,sorry for late reply as i am on vacation currently. thanks a lot for your kindsuggestion.unfortunately, i guess this hint will not work in my case,as i am using select distinct on the cds view,which will prevent limit push down ...
  • 一个问题:CDS view在HANA studio里执行,显示的耗时比在ABAP open SQL里少

    from: wang, jerrysent: monday, july 17, 2017 7:38 amhi sungheun,sorry for late reply as i am on vacation currently. thanks a lot for your kindsuggestion.unfortunately, i guess this hint will not work in my case,as i am using select distinct on the cds view,which will prevent limit push down ...
  • 能写数据后台,需要掌握哪些进阶的sql语句?

    select count(distinct user_id) as 留过言的用户总数from user_comments情境d:每日和历史累积同时去重。 假设我们想知道每日新增的留言用户数,即如果该用户以前曾留言则不计数,否则在首次留言当天计数1,这个情境比前面三种复杂点,但同样相当高频使用。 with data as ( select distinct on (user_id) user_id...
  • OushuDB入门(五)——ETL篇

    这里只为客户和产品维度创建视图,而订单维度不需要当前版本视图,因为假设业务上订单数据只能增加,不能修改,所以没有版本变化。 使用oushudb的distinct on语法去重。 distinct on ( expression )把记录根据的值进行分组,分组之后仅返回每一组的第一行。 需要注意的是,如果不指定order by子句,返回的第一条的不...
  • 原 pg查询树的简单解读

    log: parse tree: detail: {query :commandtype 1 :querysource 0 :cansettag true :utilitystmt :resultrelation 0 :hasaggs false :haswindowfuncs false :hassublinks false :hasdistincton false :hasrecursive false :hasmodifyingcte false :hasforupdate false :ctelist :rtable ( {rte :alias :eref {alias ...
  • 数据库中间件 Sharding-JDBC 源码分析 —— SQL 解析(三)之查询SQL

    { if (sqlparser.equalany(defaultkeyword.distinct, defaultkeyword.distinctrow,defaultkeyword.union)) { selectstatement.setdistinct(true); sqlparser.getlexer().nexttoken(); if (hasdistincton() && sqlparser.equalany(defaultkeyword.on)){ postgresql 独有语法: distinct on sqlparser.getlexer().next...
  • FunDA(14)- 示范:并行运算,并行数据库读取 - parallel data loading

    define query for extracting state names from aqmrpt val qrystates =aqmrptquery.map(_.state).distinct.sorted .distincton(r => r) case class...distincton(r => r) case class states(name: string) extends fdarow implicit deftostates(row: string) = states(row) val stateloader =fdastreamloa...
  • HAWQ取代传统数仓实践(十一)——维度表技术之维度合并

    create or replace view v_pa_customer_dim_latest as select customer_sk,customer_number, customer_name, customer_street_address, version,effective_date,shipping_address from (select distinct on (customer_number) customer_number,customer_sk, customer_name, customer_street_address, isdelete, ...
  • HAWQ取代传统数仓实践(六)——增加列

    effective_date from (select distinct on (customer_number) customer_number,customer_sk, customer_name, customer_street_address, customer_zip_code,customer_city, customer_state, shipping_address, shipping_zip_code,shipping_city, shipping_state, isdelete, version,effective_date from customer_dim ...
  • HAWQ取代传统数仓实践(十二)——维度表技术之分段维度

    effective_date from (select distinct on (segment_name, band_name) segment_sk,segment_name, band_name, band_start_amount, band_end_amount, isdelete,version, effective_date from annual_order_segment_dim order by segment_name,band_name, segment_sk desc) as latest where isdelete is false...
  • HAWQ取代传统数仓实践(四)——定期ETL(Sqoop、HAWQ)

    这里只为客户和产品维度创建视图,而订单维度不需要当前版本视图,因为假设业务上订单数据只能增加,不能修改,所以没有版本变化。 使用hawq的distinct on语法去重。 distinct on ( expression )把记录根据的值进行分组,分组之后仅返回每一组的第一行。 需要注意的是,如果不指定order by子句,返回的第一条的不确定...
  • Oracle在单列返回行上有所区别(1 个回答)

    出于某种原因,如果我使用:select my_view.* from my_view -- distinct on id filter where id in(select max(id) from my_view group by id) -- other arbitrary filters... order by my_view.name desc 我的表现很差,所以我开始使用这个查询:select * from my_view -- distinct on id filter leftjoin( select ...
  • 试图从每个组中只获取一行(1 个回答)

    我有五组不同的人,包括名字和姓氏。 我的目标是每个组只得到一个名字(第一个)。 当尝试使用discreteon时,我遇到了一个错误。 select distinct on (group_a) surname from table i want my table to look likegroup_a... surname_abroup_b... surname_b... thank you for your help...
  • django模板在bootstrap表上显示python字典(1 个回答)

    {2})),4326),102690)) ),process as(select distinct on(zone_from_parcels,subject_parcel_address)zone_from_parcels,subject_parcel_address,buffered_parcel_address,owner_name,dist from(select aa.address buffered_parcel_address,aa.owner_name,aa.zone_for_buff zone_from_parcels, round(st_distance(aa...

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