多條件查詢生成sql語句

剛來公司，要做一個增刪改查的功能，其中涉及到多條件查詢。對於多條件查詢，主要是涉及到如何生成sql的問題

• 在前台用js判斷是否輸入參數，把參數拼接成一個查詢條件（有2*n個分支選擇），然后傳入后台拼接成一條sql語句，如：

  function getQueryParameters(){
  var params = "where";
  var house_id = document.getElementById("house_search_id").value;	
  var house_name = document.getElementById("house_search_name").value;
  var house_location = document.getElementById("house_search_location").value;
  
  if(house_id != ""){
  	if(params == "where")
  		params = params + " id = " + house_id;
  	else
  		params = params + " and " + " id = " + house_id;
  }
  if(house_name != ""){
  	if(params == "where")
  		params = params + " name like '" + house_name + "%' ";
  	else
  		params = params + " and " + " name like '" + house_name + "%' ";
  }
  if(house_location != ""){
  	if(params == "where")
  		params = params + " location like '" + house_location + "%' ";
  	else
  		params = params + " and " + " location like '" + house_location + "%' ";
  }
  
  if(params == "where")
  	params = "";
  
  document.getElementById("queryParam").value = params;  //添加查詢參數
  docuemnt.getElementById("queryParam_fistPage").value = params;  
  document.getElementById("queryParam_prePage").value = params;
  document.getElementById("queryParam_nextPage").value = params;
  document.getElementById("queryParam_lastPage").value = params;
  document.getElementById("queryParam_edit").value = params;
          //上面這段主要是為了在查詢以后，輸入框中任然存在搜索條件，其實這么寫就可以了
          /*****************************************************************************************
          <%String param = request.getParameter("param")!= null ? "" :request.getParameter("param");%>
          <input type="text" name="param" value="<%=param%>"
          ****************************************************************************************/
  

  }

• 把所有的查詢條件都以一個不會改變查詢結果的默認值寫上，當傳入的參數不為空的時候，就把默認值替換掉

  select * from table  where  field1 = case when @param1 <> '-全部-' then @param else field1  and   field2 = case when @param2 <> '-全部-'  then @param else filed2;
  

有時間實現下第二種方法，干凈多了；