Question

I have to read a set of rows from a table(say A) containing a unique id for each row (say id_value).

Now using this id_value i have to get rows from another table (say B).

i am using java so my code is:

ResultSet rs= [ Code to get rows from table A ] ;

while(rs.next())
{
ResultSet rs2= [Code to get rows from table B using the id_value from table A using rs.getString("id_value");]; 
}

The above query if ofcourse slow as the number of rows can be more than 500 at a time in table A.

Does anybody knows a better and fast solution to this problem or how to do this in a single query ??

Answer 1

You should read up on joins in SQL: http://en.wikipedia.org/wiki/Join_(SQL)

You want to do something along these lines:

SELECT a.value_1, a.value_2, b.value_1, b.value_2
FROM table_a AS a
LEFT JOIN table_b AS b
ON a.id_value = b.table_a_id
WHERE a.value_1 = "something"

It would be easier to help you if you had actual queries, though.