JDBC根据条件查询代码

最新推荐文章于 2023-10-03 23:05:11 发布

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本文介绍了如何利用Java JDBC进行条件查询，涵盖了设置SQL语句、处理参数、执行查询和获取结果集的步骤，旨在帮助开发者更好地理解和实践数据库操作。

//1 根据条件查询
 
 public List<Message> findAllMessageBy(String name,String email,String content){
  
  String sql = " select * from message  where 1 = 1  ";
  
  String subSql = createSubSql(name,email,content);
  
  sql = sql + subSql;
  
  System.out.println(sql);
  
  
  return null;
 }

 //拼接子sql字符串
 private String createSubSql(String name,String email,String content) {
  String subSql = "  ";
  
  //判断每个参数
  boolean fname = this.isInput(name);
  
  //资深工程师
  if(true == fname) {
   subSql = subSql + " and name = '"+name+"' ";
  }
 
  boolean femail = this.isInput(email);
  if(true == femail) {
   subSql = subSql + " and email = '"+email+"' ";
  }
  
  boolean fcontent = this.isInput(content);
  if(true == fcontent) {
   subSql = subSql + " and content = '"+content+"' ";
  }
  
  return subSql;
 }
 
 //判断是否输入
 private boolean isInput (String text) {
  boolean flag = true;
  if(text == null) {
   flag = false;
  }
  
  if("".equals(text)) {
   flag = false;
  }
  
  return flag;
 }