gistfile1.txt

test=> SELECT sid, lid, COUNT(id) FROM attend GROUP BY sid, lid HAVING COUNT(id) > 1;
 sid |   lid   | count 
-----+---------+-------
 336 | ACB0030 |     2
 325 | ABF0030 |     2
(2 rows)

test=> SELECT id FROM attend WHERE sid = 336 AND lid = 'ACB0030';
  id   
-------
 60959
 60960
(2 rows)

test=> SELECT id FROM attend WHERE sid = 325 AND lid = 'ABF0030';
  id   
-------
 75117
(1 row)

test=> SELECT version();
                                               version                                                
------------------------------------------------------------------------------------------------------
 PostgreSQL 9.3.6 on x86_64-unknown-linux-gnu, compiled by gcc (Ubuntu 4.8.2-19ubuntu1) 4.8.2, 64-bit
(1 row)

test=> SELECT sid, lid, COUNT(id) FROM attend GROUP BY sid, lid HAVING COUNT(id) > 1;
 sid |   lid   | count 
-----+---------+-------
 336 | ACB0030 |     2
 325 | ABF0030 |     2
(2 rows)