sql 根据字段查询不同表

SELECT snFundType,snBusinessType,
CASE WHEN a.snFundType=10 AND a.snBusinessType =10 THEN 
(select vcPaySerialNo from aa where vcSerialNo=a.vcRelationSerialNo)
WHEN a.snFundType=11 AND a.snBusinessType =11 THEN
(select vcPaySerialNo from bb where vcSerialNo=a.vcRelationSerialNo)
END AS '姓名'

FROM cc a