Need help in writing SQL query

Question

I am facing a pecular problem in writing a sql query for below functionality: Consider below table:

---------------------------------
 AccountNumber     JobNumber
---------------------------------
    1234            1111113
    1234            1111112
    1234            1111111
    1212            1111131
    1212            1111132

I want to fetch a latest job number for account number passed to a query. For eg: If I pass 1234 as a account number, I need to get 1111113 and if I pass 1212 I should get 1111131. How to write a PL/SQL query to achieve this? We will pass multiple account number like AccountNumber IN ('1234','1212'). So for each account number I need to get latest job number.

Currently I have tried without using IN like this:

SELECT * 
  FROM (SELECT JobNumber 
          FROM TABLE1 
          WHERE AccountNumber = ?) 
 WHERE ROWNUM = 1

and in Java JDBC I am looping thorugh account number ArrayList and executing JDBC against Oracle db. But as you know it is not a feasible solution, if there are 4000 accounts performance hits.

Can you help in writing this SQL Query?

EDIT: Here latest means highest jobnumber, for eg: out of 1111113 and 1111112. 1111113 is the latest data

Answer 1

There are several ways:

SQL> create table t1(AccountNumber, JobNumber) as
  2  (
  3  select 1234,  1111113 from dual union all
  4  select 1234,  1111112 from dual union all
  5  select 1234,  1111111 from dual union all
  6  select 1212,  1111131 from dual union all
  7  select 1212,  1111132 from dual
  8  )
  9  ;

Table created




SQL> select t.AccountNumber
  2       , max(t.JobNumber) as JobNumber
  3    from t1 t
  4   where AccountNumber in (1212, 1234)  -- for example
  5   group by AccountNumber
  6  ;

ACCOUNTNUMBER  JOBNUMBER
------------- ----------
         1234    1111113
         1212    1111132

OR

SQL> select AccountNumber
  2       , JobNumber
  3    from ( select t.AccountNumber
  4                , t.JobNumber
  5                , row_number() over(partition by t.AccountNumber order by t.JobNumber desc) rn
  6             from t1 t
  7            where AccountNumber in (1212, 1234) -- for example
  8         ) t
  9  where t.rn = 1
  10  ;

ACCOUNTNUMBER  JOBNUMBER
------------- ----------
         1212    1111132
         1234    1111113

OR

SQL> select AccountNumber
  2       , JobNumber
  3    from ( select t.AccountNumber
  4                , t.JobNumber
  5                , max(JobNumber) over(partition by t.AccountNumber) mjn
  6             from t1 t
  7            where AccountNumber in (1212, 1234)   -- for example
  8         ) t
  9  where t.JobNumber = t.mjn
  10  ;

ACCOUNTNUMBER  JOBNUMBER
------------- ----------
         1212    1111132
         1234    1111113

SQL> 

Answer 2

Won't a simple max() work?

SELECT max(JobNumber)
FROM TABLE1 
WHERE AccountNumber = ?

And for multiple accounts in one query:

SELECT AccountNumber, max(JobNumber)
FROM TABLE1 
WHERE AccountNumber IN (?, ?, ?)
GROUP BY AccountNumber;

Answer 3

I would start with standard SQL first. I hope the following does it.

SELECT JobNumber 
FROM TABLE1 
WHERE id = (SELECT MIN(id)
           FROM TABLE1
           WHERE AccountNumber = ?)

Answer 4

select a, j1
from(                
 select 
      id, 
      a, 
      j, 
      first_value(j) over(partition by a order by id) j1
 from (                
    select AccountNumber a, JobNumber j, row_number() over(order by 0) id
    from table1) t
    ) t1
group by a, j1