JSP 里SQL语句怎么使用"与"把两个条件输出来？

JSP 里SQL语句如何使用"与"把两个条件输出来？？？
String sql = "select * from category where grade = 2 and 3";

grade有三级，我想把2,3级的数据全部输出来，可是为什么只能输出2级的，3的出不来
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public List<Category> getChilds(){
List<Category>categories = new ArrayList<Category>();
Connection conn=DB.getConn();
Statement stmt = DB.getStatement(conn);
String sql = "select * from category where grade = 2 and 3";
ResultSet rs = DB.getResultSet(stmt, sql);
try{
while(rs.next()){
Category c = this.getCategoryFromRs(rs);
categories.add(c);
}
}catch(SQLException e){
e.printStackTrace();
}finally{
DB.close(conn);
DB.close(stmt);
DB.close(rs);
}
return categories;
}
-----------------------------
<%
for(int i=0;i<childs.size();i++){
Category c = childs.get(i);
%>
<a href=""><%=c.getName()%></a>
<%
} 
%>

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同一个条件也要分开单独写, where grade=2 and grade=3
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探讨

同一个条件也要分开单独写, where grade=2 and grade=3

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SQL code

select * from category where grade = 2 or 3