怎样实现模糊查询？请赐教！！！100分

[star123qiu]

我怎样才能实现模糊查询？
比如说我现在有四个变量：
String id=request.getParameter("txtStu_id").trim();
String name=request.getParameter("txtName").trim();
String grade=request.getParameter("dwnGrade").trim();
String department=request.getParameter("dwnDepartment").trim();
byte[] tmpbyte=id.getBytes("ISO8859_1");
id=new String(tmpbyte);
tmpbyte=name.getBytes("ISO8859_1");
name=new String(tmpbyte);
tmpbyte=grade.getBytes("ISO8859_1");
grade=new String(tmpbyte);
tmpbyte=department.getBytes("ISO8859_1");
department=new String(tmpbyte);
要实现在数据库中的模糊查询，要求是 1，四个变量为空时，查出所有记录，2，随便一个变量有值，查出含有此内容的所有记录。
高手有礼了！

[saintKnight]

构造SQL语句时根据这四个参数是否为空来构造不行吗?
如：
String sql="select * from tablename ";
String temp="";
if(id!=nul && !id.equals("")) {
temp+=" id="+id;
}
if(name!=null && !name.equals("")) {
if(temp.length<1) {
temp+=" name='"+name+"'";
}else{
temp+=" and name='"+name+"'";
}
if(grade!=null && !grade.equals("")) {
if(temp.length<1) {
temp+=" grade='"+grade+"'";
}else{
temp+=" and grade='"+grade+"'";
}
if(department!=null && !department.equals("")) {
if(temp.length<1) {
temp+=" department='"+name+"'";
}else{
temp+=" and department='"+department+"'";
}
if(temp.length>1) {
sql+=" where "+temp;
}

[Andrawu]

String id=request.getParameter("txtStu_id").trim();
String name=request.getParameter("txtName").trim();
String grade=request.getParameter("dwnGrade").trim();
String department=request.getParameter("dwnDepartment").trim();
byte[] tmpbyte=id.getBytes("ISO8859_1");
id=new String(tmpbyte);
tmpbyte=name.getBytes("ISO8859_1");
name=new String(tmpbyte);
tmpbyte=grade.getBytes("ISO8859_1");
grade=new String(tmpbyte);
tmpbyte=department.getBytes("ISO8859_1");
department=new String(tmpbyte);

String sStr = "select * from tablename where" ;
if (!id.equals(""))
sStr +=" and (id like '%" + id + "%')";
if (!name.equals(""))
sStr += " and ( name like '%" + name + "%')";
if (!grade.equals(""))
sStr += " and ( grade like '%" + grade + "%')";
if (!department.equals(""))
sStr += " and ( department = '%" + department + "')";
if (!sStr.equals(""))
sStr = sStr.substring(5);

[Andrawu]

sorry:
有点问题。

String id=request.getParameter("txtStu_id").trim();
String name=request.getParameter("txtName").trim();
String grade=request.getParameter("dwnGrade").trim();
String department=request.getParameter("dwnDepartment").trim();
byte[] tmpbyte=id.getBytes("ISO8859_1");
id=new String(tmpbyte);
tmpbyte=name.getBytes("ISO8859_1");
name=new String(tmpbyte);
tmpbyte=grade.getBytes("ISO8859_1");
grade=new String(tmpbyte);
tmpbyte=department.getBytes("ISO8859_1");
department=new String(tmpbyte);

String sStr = "select * from tablename " ;
String sCondition = "" ;
if (!id.equals(""))
sCondition +=" and (id like '%" + id + "%')";
if (!name.equals(""))
sCondition += " and ( name like '%" + name + "%')";
if (!grade.equals(""))
sCondition += " and ( grade like '%" + grade + "%')";
if (!department.equals(""))
sCondition += " and ( department = '%" + department + "')";
if (!sCondition.equals(""))
sStr +="where "+ sCondition.substring(5);

[star123qiu]

还是不行

[zhu_liping]

没理由呀，
四个与一个是一样的呀
String sql="select * from table"
if (id==null){
sql=sql+ "where id like '%"+id+"%'";}

[chen_guo_quan]

String id=request.getParameter("txtStu_id");
String name=request.getParameter("txtName");
String grade=request.getParameter("dwnGrade");
String department=request.getParameter("dwnDepartment");
byte[] tmpbyte;
if(id!=null)
{
tmpbyte=id.trim().getBytes("ISO8859_1");
id=new String(tmpbyte);
}

if(name!=null)
{
tmpbyte=name.trim().getBytes("ISO8859_1");
name=new String(tmpbyte);
}

if(grade!=null)
{
tmpbyte=grade.trim().getBytes("ISO8859_1");
grade=new String(tmpbyte);
}

if(department!=null)
{
tmpbyte=department.trim().getBytes("ISO8859_1");
department=new String(tmpbyte);
}

String sStr = "select * from tablename " ;
String sCondition = "" ;
if (id!=null&&!id.equals(""))
sCondition +=" and ( id like '%" + id + "%')";
if (name!=null&&!name.equals(""))
sCondition += " and ( name like '%" + name + "%')";
if (grade!=null&&!grade.equals(""))
sCondition += " and ( grade like '%" + grade + "%')";
if (department!=null&&!department.equals(""))
sCondition += " and ( department = '%" + department + "')";
if (!sCondition.equals(""))
sStr +="where "+ sCondition.substring(5);

这样你先试一试，如果还不行的话，请你告诉我具体是什么情况。

[Andrawu]

String id=request.getParameter("txtStu_id")==null?"":(request.getParameter("txtStu_id").equals("null")?"":request.getParameter("txtStu_id").trim());
String name=request.getParameter("txtName")==null?"":(request.getParameter("txtName").equals("null")?"":request.getParameter("txtName").trim());
String grade=request.getParameter("dwnGrade")==null?"":(request.getParameter("dwnGrade").equals("null")?"":request.getParameter("dwnGrade").trim());
String department=request.getParameter("dwnDepartment")==null?"":(request.getParameter("dwnDepartment").equals("null")?"":request.getParameter("dwnDepartment").trim());
byte[] tmpbyte=id.getBytes("ISO8859_1");
id=new String(tmpbyte);
tmpbyte=name.getBytes("ISO8859_1");
name=new String(tmpbyte);
tmpbyte=grade.getBytes("ISO8859_1");
grade=new String(tmpbyte);
tmpbyte=department.getBytes("ISO8859_1");
department=new String(tmpbyte);

String sStr = "select * from tablename " ;
String sCondition = "" ;
if (!id.equals(""))
sCondition +=" and (id like '%" + id + "%')";
if (!name.equals(""))
sCondition += " and ( name like '%" + name + "%')";
if (!grade.equals(""))
sCondition += " and ( grade like '%" + grade + "%')";
if (!department.equals(""))
sCondition += " and ( department = '%" + department + "')";
if (!sCondition.equals(""))
sStr +="where "+ sCondition.substring(5);

试试

[mingkeming]

用like不就行了

[star123qiu]

谢谢各位仁兄，我已经成功了！