求助一列为某值时候，另一列显示为空，怎么写SQL

当currency列为RMB时，其他两列显示为空值。
[解决办法]

SELECT 
DebitAmount = (CASE CurrencyCode WHEN 'RMB' THEN NULL ELSE CreditAmount END),
CreditAmount = (CASE CurrencyCode WHEN 'RMB' THEN NULL ELSE DebitAmount END),
CurrencyCode
FROM tb

SELECT 
CreditAmount = (CASE CurrencyCode WHEN 'RMB' THEN NULL ELSE CreditAmount END),
DebitAmount = (CASE CurrencyCode WHEN 'RMB' THEN NULL ELSE DebitAmount END),
CurrencyCode
FROM tb