关于jsp数据库查询问题

[cjnsrj]

我在一个jsp查询页面中放置了三个查询条件：楼号，层号，房间号。现在我用楼号，层号，房间号查询以及用楼号，层号查询来达到显示不同的查询结果。在查询结果页面中，我用
if("房间号为空")
{
显示用楼号，层号为查询条件的查询结果；
}
else{
显示用楼号，层号，房间号为查询条件的查询结果；
}

在调试时，当未输入房间号时，点击查询按钮时，if中的语句并不执行。执行的仍是else中的内容。
这种情况如何处理。谢谢！

[伟大的左前卫]

if不执行，说明条件不满足，"房间号为空"具体你是怎么写的？

[pdvv]

if(fangHao == null || fangHao.equals("")){

}

[wsk_228]

楼上已解...

[cjnsrj]

我写的如下：
<%
String distN=request.getParameter("distNum");
String roomN=request.getParameter("roomNum");
String floorN=request.getParameter("floorNum");
%>
if(roomN==null) {
<%
try {
Class.forName("org.gjt.mm.mysql.Driver").newInstance();
String url = "jdbc:mysql://localhost/xuesheng?user=root&password=wanzhang&Unicode=true&characterEncoding=gb2312";
Connection con = DriverManager.getConnection(url);
Statement stmt=con.createStatement();
ResultSet rs;
String SqlQue="SELECT deviceuse.roomNum,devNum,useCt FROM relation,district,deviceuse where deviceuse.roomNum='"
+roomN+"' and district.distNum='"
+distN+"' and relation.floorNum='"
+floorN+"'";
//out.print(SqlQue);
rs = stmt.executeQuery(SqlQue);
while(rs.next()){
%>
<tr class="normal">
<td width="88"><%=rs.getString("roomNum")%></td>
<td width="171"><%=rs.getString("devNum")%></td>
<td width="166"><%=rs.getString("useCt")%></td>
</tr>

<% }

stmt.close();
con.close();
}
catch(SQLException ex){out.print(ex.toString());}

%>
<% } else {
<%
try {
Class.forName("org.gjt.mm.mysql.Driver").newInstance();
String url = "jdbc:mysql://localhost/xuesheng?user=root&password=wanzhang&Unicode=true&characterEncoding=gb2312";
Connection con = DriverManager.getConnection(url);
Statement stmt=con.createStatement();
ResultSet rs;
String SqlQue="SELECT deviceuse.roomNum,devNum,useCt FROM relation,district,deviceuse where deviceuse.roomNum='"
+roomN+"' and district.distNum='"
+distN+"' and relation.floorNum='"
+floorN+"'";
//out.print(SqlQue);
rs = stmt.executeQuery(SqlQue);
while(rs.next()){
%>
<tr class="normal">
<td width="88"><%=rs.getString("roomNum")%></td>
<td width="171"><%=rs.getString("devNum")%></td>
<td width="166"><%=rs.getString("useCt")%></td>
</tr>

<% }

stmt.close();
con.close();
}
catch(SQLException ex){out.print(ex.toString());}

%>
}%>

[feixue6511]

if(fangHao == null || fangHao.equals("")||fangHao.equals("0")){

}