Or you could use a table with all possible values.

Here's an example on how to create it.

CREATE TABLE Weeks(

WeekCode int,

FisrtDay date,

LastDay date

);

WITH

E(n) AS(

SELECT n FROM (VALUES(0),(0),(0),(0),(0),(0),(0),(0),(0),(0))E(n)

),

E2(n) AS(

SELECT a.n FROM E a, E b

),

E4(n) AS(

SELECT a.n FROM E2 a, E2 b

),

cteTally(n) AS(

SELECT TOP 3000 DATEADD( wk, ROW_NUMBER() OVER(ORDER BY (SELECT NULL))-1, '19950102') n

FROM E4

)

INSERT INTO Weeks

SELECT (YEAR(n) * 100) + DATEPART(ISOWK, n) WeekCode,

n AS firstday,

n + 7 AS lastday

FROM cteTally;