在SQL Server中将NULL转换为空字符串

我得到了“AltReimMethod”的空值，我想将其转换为空字符串值。问题是：

(SELECT rc.name from ReimbursementChoice rc WHERE rc.admin_id = a.admin_id AND rc.choice_id = pe.alt_payment_choice) AS 'AltReimMethod'

我试过了

(SELECT (ISNULL(rc.name,' ')) from ReimbursementChoice rc WHERE rc.admin_id = a.admin_id AND rc.choice_id = pe.alt_payment_choice) AS 'AltReimMethod'

而且

(SELECT (ISNULL(CONVERT(varchar(50),rc.name),' ')) from ReimbursementChoice rc WHERE rc.admin_id = a.admin_id AND rc.choice_id = pe.alt_payment_choice) AS 'AltReimMethod'

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它们没有显示任何错误，但我甚至没有得到任何结果。

在查询中应用IsNull，在查询中不应用IsNull：

ISNULL((SELECT rc.name from ReimbursementChoice rc WHERE 
rc.admin_id = a.admin_id AND rc.choice_id = pe.alt_payment_choice),' ') 
AS 'AltReimMethod'