SELECT 1 + RAND(checksum(NEWID()))

SELECT 1 + ABS(checksum(NEWID())) % 28

CREATE TYPE Distribution AS TABLE (EventID INT, EventProb FLOAT, CumProb FLOAT) 
GO

CREATE FUNCTION dbo.RN_MULTINOMIAL 
    (@Multinomial Distribution READONLY, @URN FLOAT)
RETURNS INT --Cannot use WITH SCHEMABINDING 
AS
BEGIN
    RETURN 
        ISNULL(
            (   SELECT TOP 1 EventID
                FROM @Multinomial
                WHERE @URN < CumProb
                ORDER BY CumProb)
            -- Handle unlikely case where URN = exactly 1.0
            ,(  SELECT MAX(EventID) 
                FROM @Multinomial))
END

DECLARE @MultinomialProbabilities Distribution

;WITH Tally (n) AS (
    SELECT TOP 28 ROW_NUMBER() OVER (ORDER BY (SELECT NULL))
    FROM sys.all_columns)
INSERT INTO @MultinomialProbabilities
SELECT n
    ,CASE n WHEN 1 THEN .6/26. WHEN 2 THEN .3 WHEN 3 THEN .1 ELSE .6/26. END
    ,CASE n WHEN 1 THEN .6*1./26. WHEN 2 THEN .3+.6*1./26. WHEN 3 THEN .4+.6*1./26. ELSE .4+.6*(n-2)/26. END
FROM Tally

SELECT * FROM @MultinomialProbabilities

DECLARE @TestNums INT = 1000
;WITH Tally (n) AS (
    SELECT TOP (@TestNums) ROW_NUMBER() OVER (ORDER BY (SELECT NULL))
    FROM sys.all_columns a CROSS JOIN sys.all_columns b)
SELECT MNRN, CountOfMNRNs=COUNT(MNRN), ActualProbability=COUNT(MNRN)/(1.*@TestNums)
FROM (
    SELECT MNRN=dbo.RN_MULTINOMIAL(@MultinomialProbabilities, URN)
    FROM Tally
    CROSS APPLY (SELECT URN=RAND(CHECKSUM(NEWID()))) a
    ) a
INNER JOIN @MultinomialProbabilities ON EventID=MNRN
GROUP BY MNRN

SELECT MNRN=dbo.RN_MULTINOMIAL(@MultinomialProbabilities, URN)
FROM (SELECT URN=RAND(CHECKSUM(NEWID()))) a