Question

I have a table yrs_order which has columns like:

header_key (primary key)
order_no
ref1
ref2
ref3

I want to get a list of all the rows for which ref1 is identical.

How can i do this?

Answer 1

If you just want a specific ref1, you can use:

select header_key from yrs_table where ref1 = 42

However, I suspect you’re after all rows that share a ref1 value. If that’s the case, the first step is to get a list of all ref1 values where there are more than one:

select ref1 from yrs_order group by ref1 having count(*) > 1

Then you can use that as a subquery to get a list of all the rows:

select header_key, ref1 from yrs_order where ref1 in (
    select ref1 from yrs_order group by ref1 having count(ref1) > 1
)

---

The following transcript shows this in action:

> CREATE TABLE PAX1 (HDR_KEY INT PRIMARY KEY NOT NULL, REF1 INT);
Table created.

> INSERT INTO PAX1 (HDR_KEY, REF1) VALUES
>>    (0,0), (1,1), (2,1), (3,1), (4,1), (5,2), (6,2), (7,3), (8,4), (9,4);
10 rows inserted.

> SELECT * FROM PAX1 ORDER BY HDR_KEY ASC;
HDR_KEY   REF1
=======   ====
      0      0
      1      1
      2      1
      3      1
      4      1
      5      2
      6      2
      7      3
      8      4
      9      4
=======   ====
10 rows fetched.

That shows the creation and population of the table, now for the query requested:

> SELECT REF1, HDR_KEY FROM PAX1 WHERE REF1 IN (
>>    SELECT REF1 FROM PAX1 GROUP BY REF1 HAVING COUNT(*) > 1
>>  ) ORDER BY REF1 ASC, HDR_KEY ASC;
REF1   HDR_KEY
====   =======
   1         1
   1         2
   1         3
   1         4
   2         5
   2         6
   4         8
   4         9
====   =======
8 rows fetched.

You can see there that the two rows with a count of one have been excluded.