sqlserver varchar轉數字進行範圍查詢

SELECT COUNT
	( [size] ) num 
FROM
	crawler_publish_property 
WHERE
	CAST ( ISNULL( [size], 0 ) AS NUMERIC ( 10, 2 ) ) >= 0 
	AND CAST ( ISNULL( [size], 0 ) AS NUMERIC ( 10, 2 ) ) < 50

Numeric(10,2)表示總位數爲10，小數點後爲2位的數，也就是說這個字段的整數位最大是8位