[SQL].判斷未滿20歲的人數是否過半

SELECT

CASE (SELECT COUNT(ACCOUNT) FROM memberdata) WHEN 0 THEN 'No'
ELSE

CASE
Floor(

( SELECT CONVERT(DECIMAL(8, 2), (SELECT COUNT(ACCOUNT) FROM memberdata WHERE Datediff("d", birthday, Getdate()) < 365.25*20) )

/

CONVERT(DECIMAL(8, 2), (SELECT COUNT(ACCOUNT) FROM memberdata))

) + 0.5

)

WHEN 0 THEN 'No' ELSE 'Yes'
END
END AS 'moreThanHalf'