sql server - Selecting correlated records from database -


i've been improving sql knowledge still failed understand how create queries.

i have following tables in sql server database:

user(id, name)

loan(id_sender, id_receiver, amount, date, date_payment)

what valid query to:

  1. select name of users have sent loans user both in 2014 , 2015
  2. select pairs (id1, id2) of users have sent loans each other

any suggestions appreciated!

edit 1:

my attempts:

1.

select name user id in (     select id_sender loan     id_receiver in (select distinct id_receiver year(date) = 2014) ,     id_receiver in (select distinct id_receiver year(date) = 2015) )

2.

select id1, id2 (     select distinct id_sender id1 loan     id_receiver in (         select distinct id_sender loan         id_receiver = ???     )     (?) )

example 1: in case date column has index, it's best not use function around column can utilize index.

select name user id in (select id_sender loan date >= '1/1/2014' , date < '1/1/2015')     , id in (select id_sender loan date >= '1/1/2015' , date < '1/1/2016')

example 2: can use self join find matches using loan table.

select     l1.id_sender id1,     l1.id_receiver id2 loan l1     inner join loan l2         on l1.id_sender = l2.id_receiver             , l2.id_sender = l1.id_receiver

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