你一定会，来帮帮我吧!(0分)

query.sql.add('select * from jxjh where specialty_year=:cc and department_year=:aa and specialty_name=:bb');
执行这段代码后为什么会出现这样的提示：
query:field 'cc' is of an unknown type
请给指点，cc,aa,bb 都是字符型变量 如果用query.sql.add('select * from jxjh where specialty_year='+quotedstr(cc));
这种查询方法另外两个字段该怎么加到WHERE条件里呢？
还有这样查询完后，我如何判断有没有查到记录呢？

query.sql.add('select * from jxjh where specialty_year=:cc and department_year=:aa and specialty_name=:bb');
...
Query.Params.ParamValues['cc'] := ...