Avg for past x months weekly

[mehaboob]

Hi, below is my data tables I have.

table1:

sku_id	dateval	sales_data
ab124	20210603	10
ab124	20210502	20
ab123	20210606	30

table2:

date_val	yr_num	yr_wk_num	day_wk_num	yr_wk_nm	day	mo_num
20200808	2020	32	6	202032	Saturday	08
20200809	2020	32	7	202032	Sunday	08
20200810	2020	33	1	202033	Monday	08
20200811	2020	33	2	202033	Tuesday	08
20200812	2020	33	3	202033	Wednesday	08

I need to take week number from table 2 comparing dateval from table1 and date_val in table 2 and do the below scenarios in looker.
1.  Rolling avg for 6 months weekly
2.  Same week prior year sales

Am new to looker. please suggest me how to achieve these scenarios in looker (LExp or view).