AWS GLUE SQL join with single row from right table-CodePudding

Im trying to join two datasets in AWS glue

Table 1(alias af):

id	data	created
1	string 1	2020-02-10
2	string 2	2020-02-11
3	string 3	2020-02-12

Table 2 (alias mp):

id	data	data2	created	foreign_key
1	string 1	json string	2020-02-10	2
2	string 2	json string	2020-02-11	3
3	string 3	json string	2020-02-12	3

What i want to do is get all rows from table 1 and select the first row from table 2 that matches the foreign key.

This is what I have currently after going through a few questions i found that i need to wrap the query with an aggregate function to let spark know that only 1 element will match this subquery.

select af.id,af.data
       (select first(mp.data)
        from mp
        where af.id= mp.foreign_key
       ) as alias1,
       
       (select first(mp.data2)
        from mp
        where af.id= mp.foreign_key
       ) as alias2
from af 
having alias 1 is not null and alias2 is not null

But this is giving me the following error:

ParseException: mismatched input 'first' expecting {')', ',', '-'}(line 3, pos 15)

Any help will be appreciated!

CodePudding user response：

Ive found a solution that works for my use case. Comment above was right the SQL was funky before.

Select af.*, mp.*
from af  join
     (select mp.*, row_number() over (partition by mp.fid order by mp.created_at) as seqnum
      from mp
     ) mp
     on af.id= mp.fid and seqnum = 1;