How to get maximum column values across a row in Teradata sql? - teradata

Question

I have a table named cnst_chrctrstc_abc with 10 columns (equ_gender1 - bb_population_flag) each row which contain numeric values (count) .
I want to get maximum 5 values out of each row across those 10 numeric columns.
The query I have looks something like the following ..
SEL
FROM
(
SEL
SUM(CASE WHEN COALESCE(act.equ_gender1,'') = COALESCE(inact.equ_gender1,'') THEN 0 ELSE 1 END ) AS equ_gender1_chg_cnt,
SUM(CASE WHEN COALESCE(act.exp_ex_bmyr1,'') = COALESCE(inact.exp_ex_bmyr1,'') THEN 0 ELSE 1 END ) AS exp_ex_bmyr1_chg_cnt,
SUM(CASE WHEN COALESCE(act.equ_age1,'') = COALESCE(inact.equ_age1,'') THEN 0 ELSE 1 END ) AS equ_age1_chg_cnt,
SUM(CASE WHEN COALESCE(act.maritalstatus1,'') = COALESCE(inact.maritalstatus1,'') THEN 0 ELSE 1 END ) AS maritalstatus1_chg_cnt,
SUM(CASE WHEN COALESCE(act.person_type1,'') = COALESCE(inact.person_type1,'') THEN 0 ELSE 1 END ) AS person_type1_chg_cnt,
SUM(CASE WHEN COALESCE(act.homeowner,'') = COALESCE(inact.homeowner,'') THEN 0 ELSE 1 END ) AS homeowner_chg_cnt,
SUM(CASE WHEN COALESCE(act.dwelling_size,'') = COALESCE(inact.dwelling_size,'') THEN 0 ELSE 1 END ) AS dwelling_size_chg_cnt,
SUM(CASE WHEN COALESCE(act.lengthofresidence,'') = COALESCE(inact.lengthofresidence,'') THEN 0 ELSE 1 END ) AS lengthofresidence_chg_cnt,
SUM(CASE WHEN COALESCE(act.childrenage0_18,'') = COALESCE(inact.childrenage0_18,'') THEN 0 ELSE 1 END ) AS childrenage0_18_chg_cnt,
SUM(CASE WHEN COALESCE(act.bb_population_flag,'') = COALESCE(inact.bb_population_flag,'') THEN 0 ELSE 1 END ) AS bb_population_flag
FROM
(SEL * FROM arc_mdm_Tbls.cnst_chrctrstc_abc WHERE load_id=1024 AND cnst_chrctrstc_end_dt='9999-12-31' (DATE))act
LEFT JOIN
(SEL * FROM arc_mdm_Tbls.cnst_chrctrstc_abc WHERE load_id=1024 AND cnst_chrctrstc_end_dt<'9999-12-31' (DATE)
QUALIFY ROW_NUMBER() OVER (PARTITION BY cnst_mstr_id ORDER BY cnst_chrctrstc_strt_ts DESC)=1
)inact
ON act.cnst_mstr_id = inact.cnst_mstr_id
)X
I know SEL GREATEST would produce the maximum value out of each row . But I want 5 top values and assign a rank to them.
Something like for some row first five columns may hold the top 5 values and for some last five i.e. homeowner to bb_population_flag may hold the top 5 values.
so if the columns and values from cnst_chrctrstc_abc look something like the following
cdi_batch_id | a | b | c | d | e | f | g | h | i |j
1024 |116|105|102|100|117|119|108|104|101|121
so the select query should return me columns j,f,e,a,g having the top 5 values.
And then I would assign a rank to them accordingly .
Should it be done using unpivot or something ?
Thanks in advance.

Answer 1

Yes, you need to unpivot your result.
Before TD14.10 you will need a list of those column names, either as a table
create table ColumnList (col varchar(128));
Insert into ColumnList('equ_gender1' );
Insert into ColumnList('exp_ex_bmyr1' );
Insert into ColumnList('equ_age1' );
Insert into ColumnList('maritalstatus1' );
Insert into ColumnList('person_type1' );
Insert into ColumnList('homeowner' );
Insert into ColumnList('dwelling_size' );
Insert into ColumnList('lengthofresidence' );
Insert into ColumnList('childrenage0_18' );
Insert into ColumnList('bb_population_flag');
or on-thy-fly using a bulky
with ColumnList as
(
select * from (select 'equ_gender1' as Col) as dt union all
select * from (select 'exp_ex_bmyr1' as Col) as dt union all
select * from (select 'equ_age1' as Col) as dt union all
select * from (select 'maritalstatus1' as Col) as dt union all
select * from (select 'person_type1' as Col) as dt union all
select * from (select 'homeowner' as Col) as dt union all
select * from (select 'dwelling_size' as Col) as dt union all
select * from (select 'lengthofresidence' as Col) as dt union all
select * from (select 'childrenage0_18' as Col) as dt union all
select * from (select 'bb_population_flag' as Col) as dt
)
Then you CROSS JOIN to unpivot:
select
col,
case col
when 'equ_gender1' then equ_gender1
when 'exp_ex_bmyr1' then exp_ex_bmyr1
when 'equ_age1' then equ_age1
when 'maritalstatus1' then maritalstatus1
when 'person_type1' then person_type1
when 'homeowner' then homeowner
when 'dwelling_size' then dwelling_size
when 'lengthofresidence' then lengthofresidence
when 'childrenage0_18' then childrenage0_18
when 'bb_population_flag' then bb_population_flag
end as Counts,
rank() over (order by Counts desc) as rnk
FROM
(
your current select
) as dt
cross join ColumnList
qualify rnk <= 5
In TD14.10 you could utilize the TD_UNPIVOT function:
SELECT Col, rank() over (order by Counts desc) as rnk
from TD_UNPIVOT(
ON (
your current select
)
USING
VALUE_COLUMNS('Counts')
UNPIVOT_COLUMN('Col')
COLUMN_LIST('equ_gender1'
,'exp_ex_bmyr1'
,'equ_age1'
,'maritalstatus1'
,'person_type1'
,'homeowner'
,'dwelling_size'
,'lengthofresidence'
,'childrenage0_18'
,'bb_population_flag')
) dt
qualify rnk <= 5;
Edit:
Additionally you might replace your LEFT JOIN with a single OLAP-function. Depending on the number of rows per cnst_mstr_id this might be more efficient as you need a ROW_NUMBER anyway:
SEL
SUM(CASE WHEN COALESCE(equ_gender1,'') = COALESCE(last_equ_gender1,'') THEN 0 ELSE 1 END ) AS equ_gender1_chg_cnt,
...
FROM
( SELECT
min(equ_gender1) OVER (PARTITION BY cnst_mstr_id ORDER BY cnst_chrctrstc_strt_ts DESC rows between 1 following and 1 following) as equ_gender1,
...
FROM arc_mdm_Tbls.cnst_chrctrstc_abc
WHERE load_id=1024
qualify cnst_chrctrstc_end_dt= date '9999-12-31'
)act