get data for a record in the past - sql

Question

I have 2 tables, table1 and table2.
What I want to achieve:
I want to return the current month info about an employee
AND
when they created an account from table 2. They might be have changed their position as of today so I want to capture info at a point in time and current on the same row.
College program table
Table 1
Name Acct_Cr_DT
a1 12/1/2018
b1 1/4/2018
c1 5/6/2018
Last Month (12/29) and current Month Data (1/29/2019). Assuming data refreshes on last day of every fiscal month.
Table 2
Name position gender Emp status FISCAL_MONTH_END_DATE
a1 Analyst M hourly 12/29/2018
b1 Intern F hourly 12/29/2018
c1 Director F hourly 12/29/2018
a1 Manager M hourly 1/29/2019
b1 Analyst F hourly 1/29/2019
c1 Director F hourly 1/29/2019
a1 was an analyst at the time of account creation.
b1 was an intern at the time of account creation.
Sample output: Need the info at the time of account creation before these got a promotion.
Name Acct_Cr_DT position gender Emp status FISCAL_MONTH_END_DATE
a1 12/1/2018 Analyst M hourly 1/29/2019
b1 1/4/2018 Intern F hourly 1/29/2019
c1 5/6/2018 Director F hourly 1/29/2019

Answer 1

If you want to return the current month info for table 1:
SELECT *
FROM YOUR_TABLE
WHERE MONTH(COLUMN_NAME) = MONTH(GETDATE())
AND YEAR(COLUMN_NAME) = YEAR(GETDATE())
However, judging your from your explanations, you need a join statement to capture info at a point in time and current on the same row. So you probably need this:
SELECT *
FROM TABLE_1 a inner join TABLE_2 b on a.id=b.id
WHERE MONTH(COLUMN_NAME) = MONTH(GETDATE())
AND YEAR(COLUMN_NAME) = YEAR(GETDATE())
Please provide sample output for further explanation.

Answer 2

Here you can try the following query.
SELECT TB1.name,Acct_Cr_DT,position,gender,Emp status,FISCAL_MONTH_END_DATE
FROM Table1 tb1
INNER JOIN Table2 tb2 ON tb1.name=tb2.name
WHERE DATEPART(YEAR,Acct_Cr_DT) = DATEPART(YEAR,FISCAL_MONTH_END_DATE) AND DATEPART(MONTH,FISCAL_MONTH_END_DATE)='12' AND DATEPART(DAY,FISCAL_MONTH_END_DATE)='29'
Getting record at the time of account creation and also the last day of the year which was the record refreshed.

Answer 3

It should be possible to solve this using the wonderful DB2 OLAP functions (aka window functions).
The following code use a subquery to pull out the first position of each employee and sort the records by fiscal end of month. The outer query then joins the results with table2 to get the employee hire date, and filters the records corresponding to the most recent fiscal end of month.
SELECT
tx.name, tx.first_position, tx.gender, tx.emp_status, tx.fiscal_month_end_date, t1.acct_cr_dt
FROM (
SELECT
t2.*,
FIRST_VALUE(t2.position) OVER(PARTITION BY t2.name ORDER BY fiscal_month_end_date) first_position,
DENSE_RANK() OVER (ORDER BY t2.fiscal_month_end_date desc) rnk
FROM table2 t2
) tx INNER JOIN table1 t1 ON t1.name = tx.name
WHERE tx.rnk = 1;
In this DB Fiddle demo, the query yields :
| name | first_position | gender | emp_status | fiscal_month_end_date | acct_cr_dt |
| ---- | -------------- | ------ | ---------- | --------------------- | ---------- |
| a1 | Analyst | M | hourly | 2019-01-29 | 2018-12-01 |
| b1 | Intern | F | hourly | 2019-01-29 | 2018-01-04 |
| c1 | Director | F | hourly | 2019-01-29 | 2018-05-06 |
NB : this a MySQL 8.0 fiddle, since there is no DB2 db fiddlde available in the wild...

Answer 4

I found the answer to this own my own.
Basically you'll have to join on Name and make sure the "Acct Create DT" is
<=FISCAL_MONTH_END_DATE" to get the info for point in time for that employee.
Now after that, create a sub-query with a LEFT JOIN on Table 2 and extract the current
"FISCAL_MONTH_END_DATE" to return current month data