Data from 3 tables having latest dates

Question

Hi,
Need some help with PL/SQL code, I need to write a code which will get data from 3 tables all with the latest date.
For a particular ACT_CODE the output of the SQL query should show data having the latest dates from 3 tables, if there is no
date in the table, it should show the remaining data (think left join will do the trick here)
Table Names:
Institution_UPDT aiu
ASQ_CONTACT ac
GR_AUTHORIZE gr
All 3 tables have ACT_Code as common                     
Column Names
INSTITUTION_UPDT aiu -- aiu.ACT_CODE,aiu.project_id as proj,aiu.UPDT_TYPE_ID, aiu.USER_ID, aiu.UPDT_DATE
ASQ_CONTACT ac -- ac.ACT_CODE as contact_code,ac.project_id,ac.first_name, ac.middle_initial,ac.last_
name,ac.title,ac.status,ac.status_date
GR_AUTHORIZE gr --gr.ACT_CODE as grad_code,gr.name, gr.title AS grad_title, gr.submit_date
The date column names are
ac.status_date,
aiu.UPDT_DATE and
gr.submit_date
Thank you everyone
appreciate your help
Jesh

Answer 1

Hi, Jesh,
user11095252 wrote:
That is correct, I want to include all the columns from ASQ_Contacts, Institution_UPDT and GR_AUTHORIZEOh! You want all columns from all three tables, not just ASQ_Contacts. That changes the problem considerably!
UNION requires that all prongs have the same number of columns, and that the datatypes of the columns match. That's no problem if we just need act_code and a date from each one. If we just need additional columns from one table, it's easy to add literal NULLs to the other prongs to serve as the additional columns. But if we need all (or even several) columns from all three tables, that's no good. So let's revert to your original idea: outer joins.
I want to display only one row which has the latest date with the most recently updated time (example:mm/dd/yyyy hr:min:sec am/pm)Yes, but what if there is a tie for the most recently updated time?
In case of a tie, the query below will pick one of the contenders arbitrarily. That may be fine with you (e.g., you may have UNIQUE constraints, making ties impossible). If you need a tie-breaker, yiou can add more columns to the analytic ORDER BY clauses.
WITH     aiu     AS
     SELECT     institution_updt.*     -- or list columns wanted
     ,     ROW_NUMBER () OVER ( PARTITION BY  act_code
                         ORDER BY        updt_date     DESC
                       ) AS r_num
FROM     institution_updt
WHERE     act_code     = :p1_act_code
AND     project_id     = :p2_project_id
,     ac     AS
     SELECT     asq_contact.*          -- or list columns wanted
     ,     ROW_NUMBER () OVER ( PARTITION BY  act_code
                         ORDER BY        status_date     DESC
                       ) AS r_num
FROM     asq_contact
WHERE     act_code     = :p1_act_code
AND     project_id     = :p2_project_id
,     gr     AS
     SELECT     gr_authorize.*          -- or list columns wanted
     ,     ROW_NUMBER () OVER ( PARTITION BY  act_code
                         ORDER BY        submit_date     DESC
                       ) AS r_num
FROM     gr_authorize
WHERE     act_code     = :p1_act_code
SELECT     *     -- or list columns wanted
FROM          aiu
FULL OUTER JOIN     ac     ON     ac.act_code     = aiu.act_code
               AND     ac.r_num     = 1
               AND     aiu.r_num     = 1
FULL OUTER JOIN     gr     ON     gr.act_code     = NVL (ac.act_code, aiu_act_code)
               AND     gr.r_num     = 1
;That's a lot of code, so there may be typos. If you'd post CREATE TABLE and INSERT statements for a few rows of sample data, I could test it.
In all places where I said "SELECT *" above, you may want to list the individual columns you want.
If you do that in the sub-queries, then you don't have to qualify the names with the table name: that's only required when saying "SELECT *" with another column (r_num, in this case).
It's more likely that you won't want to say "SELECT *" in the main query. The three r_num columns, while essential to the query, are completely useless to your readers, and you might prefer to have just one act_code column, since it will be the same for all tables that have it. But since it may be NULL in any of the tables, you'll have to SELECT it like this:
SELECT  COALESCE ( aiu.act_code
                 , ac.act_code
                 , gr_act_code
                 )  AS act_codeThe query above will actually work for multiple act_codes. You can change the condidition to something like
WHERE   act_code IN (&act_code_list)If so, remember to change it in all three sub-queries.