HiveQL: Using query results as variables - variables

Question

in Hive I'd like to dynamically extract information from a table, save it in a variable and further use it. Consider the following example, where I retrieve the maximum of column var and want to use it as a condition in the subsequent query.
set maximo=select max(var) from table;
select
*
from
table
where
var=${hiveconf:maximo}
It does not work, although
set maximo=select max(var) from table;
${hiveconf:maximo}
shows me the intended result.
Doing:
select '${hiveconf:maximo}'
gives
"select max(var) from table"
though.
Best

Answer 1

Hive substitutes variables as is and does not execute them. Use shell wrapper script to get result into variable and pass it to your Hive script.
maximo=$(hive -e "set hive.cli.print.header=false; select max(var) from table;")
hive -hiveconf "maximo"="$maximo" -f your_hive_script.hql
And after this inside your script you can use select '${hiveconf:maximo}'

Answer 2

#Hein du Plessis
Whilst it's not possible to do exactly what you want from Hue -- a constant source of frustration for me -- if you are restricted to Hue, and can't use a shell wrapper as suggested above, there are workarounds depending on the scenario.
When I once wanted to set a variable by selecting the max of a column in a table to use in a query, I got round it like this:
I first put the result into a table comprising two columns, with the (arbitrary word) 'MAX_KEY' in one column and the result of the max calculation in the other, like this:
drop table if exists tam_seg.tbl_stg_temp_max_id;
create table tam_seg.tbl_stg_temp_max_id as
select
'MAX_KEY' as max_key
, max(pvw_id) as max_id
from
tam_seg.tbl_dim_cc_phone_vs_web;
I then added the word 'MAX_KEY' to a sub-query then joined in the above table so I could use the result in the main query:
select
-- *** here is the joined in value from the table being used ***
cast(mxi.max_id + qry.temp_id as string) as pvw_id
, qry.cc_phone_vs_web
from
(
select
snp.cc_phone_vs_web
, row_number() over(order by snp.cc_phone_vs_web) as temp_id
-- *** here is the key being added to the sub-query ***
, 'MAX_KEY' as max_key
from
(
select distinct cc_phone_vs_web from tam_seg.tbl_stg_base_snapshots
) as snp
left outer join
tam_seg.tbl_dim_cc_phone_vs_web as pvw
on snp.cc_phone_vs_web = pvw.cc_phone_vs_web
where
pvw.cc_phone_vs_web is null
) as qry
-- *** here is the table with the select result in being joined in ***
left outer join
tam_seg.tbl_stg_temp_max_id as mxi
on qry.max_key = mxi.max_key
;
Not sure if this is your scenario but maybe it can be adapted. I'm 99% sure you can't just put a select statement directly into a variable in Hue though.
If I am doing something in just Hue I would probably do the temporary table and join method. But if I were using a shall wrapper anyway I would definitely do it there.
I hope this helps.