Sybase ASE looping over two tables for data calculation - sql

Question

I'm not well versed with SQL and wondering how to do this in a Syabse - ASE stored procedure. Would appreciate any guidance on this.
I have table-1 (t1) and table-2 (t2) that I need to loop over for calculations like (t1.c4+t2.c3)*2+(t1.c5+t2.c4)*5.
Steps:
Get all the rows from table-1 whose datetime column value is between a user given datetime range
For each row from table-1 get row(s) from table-2 where the datetime value from table-1 row falls between start datetime and end datetime column values in table-2
If only 1 row matched from table-2, take the values from table-1 row and table-2 row and do calculations and do step-7
If more than 1 row matched, find the row from table-2 whose start datetime is an exact match with the datetime from table-1 row
If no exact match found, flag error in table-1 row and proceed with the next row from table-1
If only one row match found, do the calculations and do step-7
Insert the calculation result into the current row of table-1
Go to step-2; until no more rows left in table-1
What is the optimal approach to do this ? Should I use cursor's Or temporary tables ?
T1
------------------------------------------------
C1 C2 C3 C4 C5 C6
------------------------------------------------
ABC 10 15 2019-03-01 00:30
XYZ 12 13 2019-03-01 01:00
DEF 5 7 2019-03-01 02:00
IJK 17 3 2019-03-02 01:00
T2
------------------------------------------------
C1 C2 C3 C4 C5
------------------------------------------------
LMN 1 5 2019-03-01 00:30 2019-03-02 00:00
OPQ 2 3 2019-03-01 01:00 2019-03-01 01:30
STU 4 2 2019-03-01 01:30 2019-03-01 03:00
KJF 3 1 2019-03-01 02:30 2019-03-01 03:00
User input: 2019-03-01 00:00 to 2019-03-01 00:30 (ABC & LMN Rows match)
Expected out:
------------------------------------------------------------
C1 C2 C3 C4 C5 C6
--------------------------------------------------------------
ABC 10 15 2019-03-01 00:30 (10*1)+(15*5)
XYZ 12 13 2019-03-01 01:00
DEF 5 7 2019-03-01 02:00
IJK 17 3 2019-03-02 01:00
User input: 2019-03-01 01:00 to 2019-03-01 01:30 (XYZ & OPQ Rows match)
Expected out:
------------------------------------------------------------
C1 C2 C3 C4 C5 C6
--------------------------------------------------------------
ABC 10 15 2019-03-01 00:30
XYZ 12 13 2019-03-01 01:00 (12*2)+(13*3)
DEF 5 7 2019-03-01 02:00
IJK 17 3 2019-03-02 01:00
User input: 2019-03-01 23:59 TO 2019-03-02 01:00 (IJK row & No matching rows in t2)
Expected output:
----------------------------------------------------
C1 C2 C3 C4 C5 C6
----------------------------------------------------
ABC 10 15 2019-03-01 00:30
XYZ 12 13 2019-03-01 01:00
DEF 5 7 2019-03-01 02:00
IJK 17 3 2019-03-02 01:00 No matching row
User input: 2019-03-01 01:30 TO 2019-03-01 02:30 (DEF row)
Expected output:
Though DEF falls in STU & KJF date range start dates i.e. C4 col of either rows match with DEF datetime exactly
----------------------------------------------------
C1 C2 C3 C4 C5 C6
----------------------------------------------------
ABC 10 15 2019-03-01 00:30
XYZ 12 13 2019-03-01 01:00
DEF 5 7 2019-03-01 02:00 No unique match
IJK 17 3 2019-03-02 01:00