在 SQL Viia 递归查询中组合行

Question

我有下表。

Animal  Vaccine_Date    Vaccine
Cat     2/1/2016        y
Cat     2/1/2016        z
Dog     2/1/2016        z
Dog     1/1/2016        x
Dog     2/1/2016        y

我希望得到如下所示的结果。

Animal  Vaccine_Date    Vaccine
Dog     1/1/2016        x
Dog     2/1/2016        y,z
Cat     2/1/2016        y,z

我有以下代码，它是通过我在“Combine(concatenate) rows based on dates via SQL”的其他帖子提供的

WITH RECURSIVE recCTE AS
(
    SELECT 
        animal, 
        vaccine_date,
        CAST(min(vaccine) as VARCHAR(50)) as vaccine, --big enough to hold concatenated list 
        cast (1 as int) as depth --used to determine the largest/last group_concate (the full group) in the final select
    FROM TableOne

    GROUP BY 1,2


    UNION ALL

    SELECT 
        recCTE.animal,
        recCTE.vaccine_date,
        trim(trim(recCTE.vaccine)|| ',' ||trim(TableOne.vaccine)) as vaccine,
        recCTE.depth + cast(1 as int) as depth
    FROM recCTE 
        INNER JOIN TableOne ON
            recCTE.animal = TableOne.animal AND
            recCTE.vaccine_date =  TableOne.vaccine_date and
           TableOne.vaccine > recCTE.vaccine

           WHERE recCTE.depth < 5


)

--Now select the result with the largest depth for each animal/vaccine_date combo
SELECT * FROM recCTE
QUALIFY ROW_NUMBER() OVER (PARTITION BY animal,vaccine_date ORDER BY depth desc) =1

但这会导致以下结果。

Animal  Vaccine_Date    vaccine     depth
Cat     2/1/2016        y,z,z,z,z   5
Dog     1/1/2016        x           1
Dog     2/1/2016        y,z,z,z,z   5

“z”不断重复。这是因为代码中的任何内容都超过了最低限度的疫苗。为了解决这个问题，代码更改为以下内容。

WITH RECURSIVE recCTE AS
(
    SELECT 
        animal, 
        vaccine_date,
        CAST(min(vaccine) as VARCHAR(50)) as vaccine, --big enough to hold concatenated list 
        cast (1 as int) as depth, --used to determine the largest/last group_concate (the full group) in the final select
        vaccine as vaccine_check
    FROM TableOne

    GROUP BY 1,2,5


    UNION ALL

    SELECT 
        recCTE.animal,
        recCTE.vaccine_date,
        trim(trim(recCTE.vaccine)|| ',' ||trim(TableOne.vaccine)) as vaccine,
        recCTE.depth + cast(1 as int) as depth,
        TableOne.vaccine as vaccine_check
    FROM recCTE 
        INNER JOIN TableOne ON
            recCTE.animal = TableOne.animal AND
            recCTE.vaccine_date =  TableOne.vaccine_date and
           TableOne.vaccine > recCTE.vaccine and
           vaccine_check <> recCTE.vaccine_check 

           WHERE recCTE.depth < 5


)

--Now select the result with the largest depth for each animal/vaccine_date combo
SELECT * FROM recCTE
QUALIFY ROW_NUMBER() OVER (PARTITION BY animal,vaccine_date ORDER BY depth desc) =1

但是，结果如下。

Animal  Vaccine_Date    vaccine depth   vaccine_check
Cat     2/1/2016        y       1       y
Dog     1/1/2016        x       1       x
Dog     2/1/2016        y       1       y

代码中缺少什么以获得以下所需的结果。

Animal  Vaccine_Date    Vaccine
Dog     1/1/2016        x
Dog     2/1/2016        y,z
Cat     2/1/2016        y,z

Answer 1

嗯。我手头没有 Teradata，但这是该项目的一个主要缺点（在我看来）。我认为这对你有用，但可能需要一些调整：

with tt as (
      select t.*,
             row_number() over (partition by animal, vaccine_date order by animal) as seqnum
             count(*) over (partition by animal, vaccine_date) as cnt
     ),
     recursive cte as (
      select animal, vaccine_date, vaccine as vaccines, seqnum, cnt
      from tt
      where seqnum = 1
      union all
      select cte.animal, cte.dte, cte.vaccines || ',' || t.vaccine, tt.seqnum, tt.cnt
      from cte join
           tt
           on tt.animal = cte.animal and
              tt.vaccine_date = cte.vaccine_date and
              tt.seqnum = cte.seqnum + 1
     )
select cte.*
from cte
where seqnum = cnt;

Answer 2

如果您的 Teradata Database 版本为 14.10 或更高版本，则它支持 XML 数据类型。这也意味着支持 XMLAGG 函数，这对您的情况很有用，并且可以让您避免递归。

检查XMLAGG 函数是否存在，该函数作为 UDF 随 XML Services 一起安装：

SELECT * FROM dbc.FunctionsV WHERE FunctionName = 'XMLAGG'

如果是这样，那么查询将如下所示：

SELECT
  animal,
  vaccine_date
  TRIM(TRAILING ',' FROM CAST(XMLAGG(vaccine || ',' ORDER BY vaccine) AS VARCHAR(10000)))
FROM
  tableone
GROUP BY 1,2

我无法测试此 atm，但我相信这应该可以进行细微调整。

Answer 3

我能够使用以下 SQL 获得所需的结果。这似乎根本不是很有效，也不是动态的。但是，我可以根据需要添加额外的子查询，以按日期按动物组合更多疫苗。

select 
qrya.animal
,qrya.vaccine_date
,case when qrya.vac1 is not null then qrya.vac1 else null end ||','||case when qrya.animal=qryb.animal and qrya.vaccine_date=qryb.vaccine_date then qryb.Vac2 else 'End' end as  vaccine_List
from
(
select

qry1.Animal
,qry1.Vaccine_Date

,case when qry1.Vaccine_Rank = 1  then qry1.vaccine end as Vac1


from
(
select 
animal
,vaccine_date
,vaccine
,row_number() over (partition by animal,vaccine_date order by vaccine) as Vaccine_Rank
from TableOne
) as qry1

where vac1 is not null

group by qry1.Animal,
qry1.Vaccine_Date
,case when qry1.Vaccine_Rank = 1  then qry1.vaccine end 
) as qrya
join
(
select

qry1.Animal
,qry1.Vaccine_Date

,case when qry1.Vaccine_Rank = 2  then qry1.vaccine end as Vac2


from
(
select 
animal
,vaccine_date
,vaccine
,row_number() over (partition by animal,vaccine_date order by vaccine) as Vaccine_Rank
from TableOne
) as qry1

where vac2 is not null

group by qry1.Animal,
qry1.Vaccine_Date
,case when qry1.Vaccine_Rank = 2  then qry1.vaccine end 
) as qryb
on qrya.Animal=qryb.Animal