Selecting first occurrence in SAS SQL - sql

Question

I'm trying to select the first occurrence of record on two conditions but have been in vain. Here's my codes:
PROC SQL;
CREATE TABLE table1 AS
SELECT user_id, type, date, money
FROM table2
WHERE date IN (SELECT MIN(date)
FROM twice_transaction
GROUP BY user_id,type);
For example the original table looks like this(table2)
user type date money
user1 type1 1/10/2012 money1
user1 type1 2/20/2012 money2
user1 type2 1/15/2012 money3
user1 type2 2/30/2012 money4
user2 type1 3/28/2012 money5
user2 type2 2/14/2012 money6
user2 type2 4/13/2012 money7
but I want only: (table1)
user1 type1 1/10/2012 money1
user1 type2 1/15/2012 money3
user2 type1 3/28/2012 money5
user2 type2 2/14/2012 money6
How should I modify/code for my end result? thanks!

Answer 1

There are a couple of ways to do this with SQL. The comment by #NoDisplayName shows you a more traditional SAS way of accomplishing this.
CREATE TABLE table1 AS
SELECT a.user_id, a.type, a.date, a.money
FROM table2 as a
INNER JOIN
SELECT (user_id, type, min(date) as date from table2 group by user_id, type) as b
on a.user_id = b.user_id
and a.type = b.type
and a.date = b.date;
What I am doing here is creating an inner select to get the min date by user_id and type. Then I use an inner join to select only the records from the from the first table that line up with the second.

Answer 2

Use the HAVING clause is also an option.
data have;
informat usert type $8. date mmddyy10. money $8.;
format date date9.;
input usert type date money;
cards;
user1 type1 1/10/2012 money1
user1 type1 2/20/2012 money2
user1 type2 1/15/2012 money3
user1 type2 2/28/2012 money4
user2 type1 3/28/2012 money5
user2 type2 2/14/2012 money6
user2 type2 4/13/2012 money7
;
run;
proc sql;
create table want as
select usert, type, date, money
from have
group by usert, type
having date=min(date);
quit;