select 语句经典小算法

/*返回按条件的搜索*/

public ResultSet getBookTypeList(Connection con,BookType bookType) throws Exception {
  StringBuffer sb_Sql=new StringBuffer("select * from t_bookType");
  String search_BookTypeName=bookType.getBookTypeName();
  if(StringUtil.isEmpty(search_BookTypeName)==false){
   sb_Sql.append(" and bookTypeName like '%"+search_BookTypeName+"%'");
  }
  PreparedStatement pstmt=con.prepareStatement(sb_Sql.toString().replaceFirst("and","where"));
  return pstmt.executeQuery();
 }

 

对于以上代码，当有多个判断条件时，如下：

 

if(条件1)sb.append(" where bookTypeName ……")

if（条件2）sb.append(" and bookTypeDetail ……")

 

if()…………

 

会有很好的效果。