Это даст вам 10000 строк в указанном формате.
DECLARE @Numbers TABLE
(
n INT PRIMARY KEY
);
WITH E00(N) AS (SELECT 1 UNION ALL SELECT 1), --2
E02(N) AS (SELECT 1 FROM E00 a, E00 b), --4
E04(N) AS (SELECT 1 FROM E02 a, E02 b), --16
E08(N) AS (SELECT 1 FROM E04 a, E04 b), --256
E16(N) AS (SELECT 1 FROM E08 a, E08 b) --65,536
INSERT INTO @Numbers
SELECT TOP 10000 ROW_NUMBER() OVER (ORDER BY (SELECT 0))
FROM E16
SELECT CAST((SELECT TOP 20 CHAR(CASE
WHEN Abs(Checksum(Newid()))%2 = 0 THEN 65
ELSE 97
END + Abs(Checksum(Newid()))%26)
FROM @Numbers n1
WHERE n1.n >= -n2.n /*So it gets re-evaluated for each row!*/
FOR XML PATH('')) AS CHAR(20))
FROM @Numbers n2