根据联接表的日期列之一的最大日期值执行更新（Oracle）

Question

I was trying to update the "description" column of Table_H according to its complex relationship with other tables. Here is the original (somewhat obfiscated) query:

        UPDATE Table_H hb SET 
        description = 'New Description'
        where exists
        (select 1
        from TABLE_J j, TABLE_I i, TABLE_K k, Table_H h, TABLE_M m
        where j.Alt_id = i.Alt_id
        and i.id=k.id
        and k.id=h.id
        and k.Alt_id = m.Alt_id
        and j.Activity='Activity A'
        and h.description = 'Old Description'
        and h.id=hb.id
        );

The problem with this query was that it updated too many Table_H rows (as those rows related to the rows of the other tables in the query). This was because Table_H had multiple rows that were identical with the exception of the Table_H.date field, which was always unique. What I actually needed to do was update only the Table_H rows with the MAX Table_H.date field.

I have not been able to find an old thread that is particularly close to my situation. Obviously I have to introduce the Table_H.Date column but not sure how to proceed. I would be grateful for any response. Thank you

Answer 1

I hope you need something like this.

UPDATE Table_H hb
SET description = 'New Description'
WHERE EXISTS
  (SELECT 1
  FROM TABLE_J j,
    TABLE_I i,
    TABLE_K k,
    Table_H h,
    TABLE_M m
  WHERE j.Alt_id    = i.Alt_id
  AND i.id          =k.id
  AND k.id          =h.id
  AND k.Alt_id      = m.Alt_id
  AND j.Activity    ='Activity A'
  AND h.description = 'Old Description'
  AND h.id          =hb.id
  )
AND hb.date_t IN
  ( SELECT MAX(Date_t) FROM Table_H
  );

Here Date_t is your date column

Answer 2

I appreciate the responses. I found out a way to do this without directly using the date column. I used the max(table_h.id) column instead (I realized the max id corresponded directly to the max(table_h.date) and this made the query earlier to write). Here is the solution. I apologize if this is not a very good learning opportunity for others in stackoverflow:

UPDATE Table_H hb
SET description = 'New Description'
WHERE EXISTS
  (SELECT 1 from
(select max(h.id) hid, k.Alt_id
FROM TABLE_J j,
TABLE_I i,
TABLE_K k,
Table_H h,
TABLE_M m
WHERE j.Alt_id    = i.Alt_id
AND i.id          =k.id
AND k.id          =h.id
AND k.Alt_id      = m.Alt_id
AND j.Activity    ='Activity A'
AND h.description = 'Old Description'
GROUP BY k.alt_id) abc
WHERE abc.hid = hb.id
)