Big query analytical function not giving expected results - google-cloud-platform

Question

I am trying to write a sql in bigquery and I have a requirement to filter records based on a group by column and another column in the table
what I mean is I want to check if the group by column(column name:mnt) has more than one row then I have to check if col2 (col name: zel) value, then I have to apply a filter saying col2 ='X' and only pass that record else pass i.e dont filter the records if the col1 has only distinct one value per group
So I have written a sql to do this I have used row_number as well as rank , dense rank function but I noticed the value of rank and dense rank and row number functions return same value for a group
Please see the below code
#standardsql
with t1 as (SELECT mnt,
case when rank() over (partition by ltrim(rtrim(mnt)) order by
ltrim(rtrim(mnt)) asc) >1 then 'Y' else 'N' end
as flag,
rank() over (partition by mnt order by mnt) as rn,
dense_rank() over (partition by mnt order by mnt) as drn, FROM
projectname.datasetname.tablename1),
t2 as ( SELECT
mnt,
rel,
lif,
lts,
lokez FROM projectname.datasetname.tablename2
WHERE lts <> "" AND _PARTITIONTIME = TIMESTAMP(CURRENT_DATE()) ) ,
t3 as (SELECT
lif,
lifn,
lts,
par FROM `projectname.datasetname.tablename3`)
,t4 as (SELECT rcv FROM `projectname.datasetname.tablename4` WHERE mes
= 'PRO')
select * from (
SELECT t1.mnt as mnt,
t1.flag,
t1.rn,
t1.drn
t2.rel as zel,
t2.lokez as ZLOEKZ,
t4.rcv as Zrcv
FROM t1 left join t2 on replace(t1.mnt, '00000000', '') =
REPLACE(t2.mnt, '00000000', '') AND t1.lif = t2.lif and t2.lts <> ""
and
case when t1.flag = 'Y' and t2.rel ='X' then 1
when (t1.flag ='N' and t2.rel=t2.rel) or (t1.flag ='N' and t2.rel
is null) then 1
when t1.flag = 'Y' and t2.rel <>'X' then 2
else 3
end = 1
left join t3 ON t1.lif = t3.lif AND t2.lts = t3.lts AND
t3.par = 'BA' left join t4 on t4.rcv = t3.lifn and t2.lokez is null )
where ZLOEKZ is null order by mnt
As you can see I am using a case statement and even it seems to be not working fine. I am pasting the case condition below again
case when t1.flag = 'Y' and t2.rel ='X' then 1
when (t1.flag ='N' and t2.rel=t2.rel) or (t1.flag ='N' and
t2.rel
is null) then 1
when t1.flag = 'Y' and t2.rel <>'X' then 2
else 3
end = 1
But the expected record count did not match so I added the above sql lines to see if my analytical functions were giving me result I wanted
rank() over (partition by mnt order by mnt) as rn,
dense_rank() over (partition by mnt order by mnt) as drn
strangely for same mnt number the rank , dense rank and row_number function are assigning the same value what am i doing wrong here.
mnt flag rn drn rel lokez rcv
100 N 1 1 X abc 123
100 N 1 1 null xyz 123
100 N 1 1 null def 234
This is my output
I mean as per my code for same mnt number I am seeing flag set to N instead of Y and for the rank and dense rank are giving me same number for all 3 mnt it is generating 1 instead of 123 (note for rank function I understand) but dense rank should not do that
I tried to convey the issue as efficiently as I could please let me know if there is any clarifications I can provide.
any help appreciated
thanks

Answer 1

SELECT * EXCEPT(ct) FROM (
SELECT *, COUNT() OVER(PARTITION BY mnt) AS ct
) WHERE ct=1 or zel='X'
This is the code snippet for the problem you mentioned. Use this in your code according to the logic.