SQL: delete command for duplicate rows for any particular user

Question

Hello Experts,
I've a table like below, where 'X' is the primary key.
X Y Z
a | p | amit
b | q | amit
c | r | amit
d | p | amit
e | s | amit
f | p | manish
g | t | manish
h | p | akash
Objective:
Find and delete all the rows who has duplicates (for 'Y') for user 'amit'. Here, 'p' is given as an example. We don't know what the actual duplicate value is.
Expected Result:
rows 'a' and 'd' should be deleted
SQL:
===
select Y, count(*) from T where Z='amit'
group by Y
having count(Y) >1
This query works to get the duplicates and the total count.
However, how to delete these rows from actual table is the question. Please note that I need to run this query through a JDBC program.
Thanks,

Answer 1

You could try
delete from tableb
  where x not in ( select max(s.x)
                    from tableb s
                    group by s.y, s.z);The easiest way I've found to build these sort of statements is to write a select first which gives you the records you want ( or not want in this case ). Then to write the delete round that statement.
Edited by: Nigel Ren on 07-May-2011 01:23