SQL Query merge - sql

Question

I am working on a scenario where for example I need to search customers by telephone and/or email address.
for example
if :lv_telephone <> '' then
lt_phone = select a.customer from customer_master a inner join telephone as b on a.address = b.address;
end if;
if :lv_email <> '' then
lt_email = select a.customer from customer_master a inner join email as b on a.address = b.address;
end if;
DB - HANA.
I want to create one final result merging both email and phone table only if they both have result set. Any pointers on how to do it?

Answer 1

You may avoid any script logic and "merge" your results in a plain SQL with conditions on variables (regardless of their source):
select a.customer
from customer_master a
left join telephone t
on a.address = t.address
and lv_telephone != ''
left join email e
on a.address = e.address
and lv_email != ''
where 1 = 1
/*Applies only when lv_telephone is not ''*/
and map(lv_telephone, '', '', t.address) is not null
/*Applies only when lv_email is not ''*/
and map(lv_email, '', '', e.address) is not null
This may also be adapted if you need to filter by passed values: compare with variable value instead of null. If variables come from SQLScript code, this can be embedded into SQLScript code. If they come from outside (e.g. some external language communicating with your DB), you may use bind variables and plain SQL withour additional script wrapper.
Below is example with standard SAP tables:
create procedure test_sp ( in iv_tel nvarchar(10), in iv_email nvarchar(10))
as
begin
select b.*
from sapdbh.t006 as b
left join sapdbh.t006a as t
on b.msehi = t.msehi
and t.spras = 'R'
and :iv_tel != ''
left join sapdbh.t006t as e
on b.dimid = e.dimid
and e.spras = 'R'
and :iv_email != ''
where 1 = 1
and case
when :iv_tel != ''
then t.msehi
else ''
end is not null
and case
when :iv_email != ''
then e.dimid
else ''
end is not null
;
end;
And execution plans below (I didn't use mandt in join so you may observe results are multiplied when join is introduced):
With call test_sp('', ''); one table accessed.
With call test_sp('X', ''); two tables accessed.
With call test_sp('X', 'X'); three tables accessed.