What is the best way to do this? I am stuck!!

Question

I have a block with this, PLEASE help! I am writing a plsql package that is going to create a custom table everything is going fine EXCEPT that I don’t know what will be the best way to do this. Please point me in the right direction a function or something:
I have three tables:
My custom table SZSLIFE
Two existing tables in my DATABASE:
SGBSTDN,
SLRRASG
For this pidm (primary key). I have the following records in the SLRRASG table:
SLRRASG_PIDM     SLRRASG_BLDG_CODE     SLRRASG_ROOM_NUMBER     SLRRASG_TERM_CODE     SLRRASG_RRCD_CODE     SLRRASG_BEGIN_DATE
139203     ADD     103     200490     RCOM     09/02/2004
139203     ADD     103     200510     RCOM     01/24/2005
139203     BLA     001     200390     RCOM     09/03/2003
139203     BLA     001     200410     RCOM     01/25/2004
139203     HRK     101     200690     RCOM     08/31/2006
139203     RIV     11     200590     RCOM     09/01/2005
And I have the following records in the SGBSTDN table.
SGBSTDN_PIDM     SGBSTDN_TERM_CODE_EFF     SGBSTDN_STST_CODE     SGBSTDN_LEVL_CODE     SGBSTDN_STYP_CODE     SGBSTDN_TERM_CODE_MATRIC
139203     200390     AS     UG     C     200390
139203     200410     AS     UG     C     200390
139203     200590     DW     UG     C     200390
139203     200610     IS     UG     C     200390
139203     200660     AS     UG     C     200390
139203     200690     AS     UG     E     200390
139203     200710     IS     UG     C     200390
So far I have been able to insert the following records in my custom table. This data is coming from the sgbstdn table
SZSLIFE_PIDM     SZSLIFE_SLRRASG_TERM_CODE     SZSLIFE_STUDENT_STATUS_CODE     SZSLIFE_STUDENT_STATUS_DESC     SZSLIFE_STUDENT_TYPE_CODE     SZSLIFE_STUDENT_TYPE_DESC     SZSLIFE_STUDENT_LEVEL_CODE     SZSLIFE_STUDENT_LEVEL_DESC
139203     200390     AS     Active     C     Continuing     UG     Undergraduate
139203     200410     AS     Active     C     Continuing     UG     Undergraduate
139203     200590     DW     Directed to Withdraw     C     Continuing     UG     Undergraduate
139203     200610     IS     Inactive     C     Continuing     UG     Undergraduate
139203     200660     AS     Active     C     Continuing     UG     Undergraduate
139203     200690     AS     Active     E     Readmit/Re-entry     UG     Undergraduate
139203     200710     IS     Inactive     C     Continuing     UG     Undergraduate
NOW the question is: I need to insert the rows from the term 200490 and 200510 because there is data in the slrrasg table for those terms BUT the data that I need to insert is coming from the SGBSTDN table and there is not data for those terms in sgbstdn, so my user is telling my that it is okay to insert the previous term from sgbstdn for example: for the term 200490 I need to insert trhe 200490 in the szslife_slrrasg_term_code but I also need to insert the row from the 200390(previous one) from SGBSTDN.
The same for 200510 insert 200510 in szslife_slrrasg_term_code but the rows from the term 200410 in SGBSTDN.
Please give some ideas of how to do this. I will highly appreciate.

Answer 1

Thank you very much for your answer, I have to confess that I am confused, never code this way. It looks very cool, I will like to learn this technique.
This is what I have using my tables and my columns.
What is the idea here? create a table 4 on the fly with all the coulmns that I need? This is what I have but I don't thing is going to work.
2) do you need to have the same number of columns in the select like when you do a UNION?
WITH tab1 AS
(SELECT
sgbstdn_term_code_eff,
sgbstdn_term_code_eff,
sgbstdn_stst_code,
sgbstdn_styp_code,
sgbstdn_levl_code,
sgbstdn_resd_code
FROM sgbstdn
UNION ALL
SELECT
slrrasg_term_code,
slrrasg_bldg_code ,
slrrasg_room_number,
slrrasg_rrcd_code ,
slrrasg_begin_date ,
slrrasg_end_date,
slrrasg_ascd_code
FROM SLRRASG
UNION ALL
SELECT
szslife_slrrasg_term_code,
szslife_student_status_code,
szslife_student_type_code,
szslife_student_level_code,
szslife_student_level_desc,
szslife_residency_code,
szslife_building_code,
szslife_room_number,
szslife_assignment_begin_date,
szslife_assignment_end_date,
szslife_assignment_status
FROM szslife
UNION ALL
SELECT NEW_TABLE ---QUESTION what I need to select here all the columns from table 1,2,3?
tab2 AS
(SELECT
sgbstdn_term_code_eff,
sgbstdn_term_code_eff,
sgbstdn_stst_code,
sgbstdn_styp_code,
sgbstdn_levl_code,
sgbstdn_resd_code
FROM sgbstdn
UNION ALL
SELECT
szslife_slrrasg_term_code,
szslife_student_status_code,
szslife_student_type_code,
szslife_student_level_code,
szslife_student_level_desc,
szslife_residency_code,
szslife_building_code,
szslife_room_number,
szslife_assignment_begin_date,
szslife_assignment_end_date,
szslife_assignment_status
FROM szslife
UNION ALL
SELECT NVL(tab2.a,lag(tab1.a) over(ORDER BY tab1.a))
FROM tab1, tab2
WHERE tab1.a = tab2.a(+)
I will apprecite your help, I did look in my books for a similar example but not luck.
Rogelio