多條件查詢(xún)，會(huì)有N個(gè)判斷， 根據(jù)每種條件查詢(xún)寫(xiě)方法， 會(huì)頭變得越來(lái)越大， 這個(gè)時(shí)候我們可以用下面這種方法，只需分別判斷單個(gè)值就ok
String names = request.getParameter("names");
String blood = request.getParameter("blood");
String search = "";
if(names != null && names != ""){
search += " and names like '%"+names+"%' ";
}
if(blood != null && blood != ""){
search += " and blood = '"+blood+"' ";
}
if(!search.equals("")){
search = " where " + search.substring(4);
System.out.println(search);
}
String sql = "select * from students " + search + " order by id desc";
//最終可生成結(jié)果
//where names like '%小紅%' and blood = 'AB'