I want to insert date if not exist in another table

 Declare @weekstart date
 Declare @weekend date

Set @weekstart='2019-01-20'
Set @weekend='2019-01-26'

Declare @day1 date
Declare @day2 date
Declare @day3 date
Declare @day4 date
Declare @day5 date
Declare @day6 date
Declare @day7 date

if (@weekstart in (SELECT [date] FROM [tbl_holidaies])) Begin Set @day1=@weekstart END else Begin Set @day1=null End;
if ((DATEADD(dd, 1, @weekstart)) Not in (SELECT [date] FROM [tbl_holidaies])) Begin Set @day1=(DATEADD(dd, 1, @weekstart)) END else Begin Set @day1=null End;
if ((DATEADD(dd, 2, @weekstart)) Not in (SELECT [date] FROM [tbl_holidaies])) Begin Set @day1=(DATEADD(dd, 2, @weekstart)) END else Begin Set @day1=null End;
if ((DATEADD(dd, 3, @weekstart)) Not in (SELECT [date] FROM [tbl_holidaies])) Begin Set @day1=(DATEADD(dd, 3, @weekstart)) END else Begin Set @day1=null End;
if ((DATEADD(dd, 4, @weekstart)) Not in (SELECT [date] FROM [tbl_holidaies])) Begin Set @day1=(DATEADD(dd, 4, @weekstart)) END else Begin Set @day1=null End;
if ((DATEADD(dd, 5, @weekstart)) Not in (SELECT [date] FROM [tbl_holidaies])) Begin Set @day1=(DATEADD(dd, 5, @weekstart)) END else Begin Set @day1=null End;
if (@weekend in (SELECT [date] FROM [tbl_holidaies])) Begin Set @day1=@weekend END else Begin Set @day1=null End;

Insert Into  tbl_week_sched ([1],[2],[3],[4],[5],[6],[7]) values (@day1,@day2,@day3,@day4,@day5,@day6,@day7)

[tbl_holidaies]

date
2019-01-04
2019-01-06
2019-01-11
2019-01-13
2019-01-18
2019-01-20
2019-01-25
2019-01-27
2019-02-01
2019-02-03

id	1	2	3	4	5	6	7
1	NULL	NULL	NULL	NULL	NULL	NULL	NULL