在 Java 中处理多个过滤器 -MySql

Question

共有三个过滤器 Class、Section 和 Date。现在有七种可能：

1- 用户输入类

2-)用户输入部分

3-)用户输入日期

4-) 用户输入日期和类别

等等……

我编写了以下代码来处理 java 中的这些可能性：

if( mySection.equals("0") && myClass.equals("0") && ( FDate.trim().compareTo("")==0 || TDate.trim().compareTo("")==0    ) )
        {
        out.println("Note: Please provide valid filteration attributes. Atleast one filter is required.");
        return;
        }



        if( !mySection.equals("0") && myClass.equals("0") && ( FDate.trim().compareTo("")==0 || TDate.trim().compareTo("")==0    ) )
        {
            Query = "select st.rollno, concat(st.firstname,' ',st.midname,' ',st.lastname), st.level, st.section, st.rfidtag, sc.schoolname, sa.time, date_format(sa.time,'%T') from AAV.studentattendence sa, AAV.Students st, AAV.Schools sc where sa.studentindexptr=st.indexptr and sc.indexptr=st.schoolindexptr and st.section='"+mySection+"'";
        }

        if( !mySection.equals("0") && !myClass.equals("0") && ( FDate.trim().compareTo("")==0 || TDate.trim().compareTo("")==0    ) )
        {
            Query = "select st.rollno, concat(st.firstname,' ',st.midname,' ',st.lastname), st.level, st.section, st.rfidtag, sc.schoolname, sa.time, date_format(sa.time,'%T') from AAV.studentattendence sa, AAV.Students st, AAV.Schools sc where sa.studentindexptr=st.indexptr and sc.indexptr=st.schoolindexptr and st.section='"+mySection+"' and st.level='"+myClass+"' ";
        }


        if( mySection.equals("0") && !myClass.equals("0") && ( FDate.trim().compareTo("")==0 || TDate.trim().compareTo("")==0    ) )
        {
            Query = "select st.rollno, concat(st.firstname,' ',st.midname,' ',st.lastname), st.level, st.section, st.rfidtag, sc.schoolname, sa.time, date_format(sa.time,'%T') from AAV.studentattendence sa, AAV.Students st, AAV.Schools sc where sa.studentindexptr=st.indexptr and sc.indexptr=st.schoolindexptr and st.level='"+myClass+"' ";
        }


        if( mySection.equals("0") && myClass.equals("0") && ( !(FDate.trim().compareTo("")==0) && !(TDate.trim().compareTo("")==0)    ) )
        {
            Query = "select st.rollno, concat(st.firstname,' ',st.midname,' ',st.lastname), st.level, st.section, st.rfidtag, sc.schoolname, sa.time, date_format(sa.time,'%T') from AAV.studentattendence sa, AAV.Students st, AAV.Schools sc where sa.studentindexptr=st.indexptr and sc.indexptr=st.schoolindexptr and date_format(time,'%Y-%m-%d %T') between '"+FromDate+"'  and '"+ToDate+"'";
        }


        if( mySection.equals("0") && !myClass.equals("0") && ( !(FDate.trim().compareTo("")==0) && !(TDate.trim().compareTo("")==0)    ) )
        {
            Query = "select st.rollno, concat(st.firstname,' ',st.midname,' ',st.lastname), st.level, st.section, st.rfidtag, sc.schoolname, sa.time, date_format(sa.time,'%T') from AAV.studentattendence sa, AAV.Students st, AAV.Schools sc where sa.studentindexptr=st.indexptr and sc.indexptr=st.schoolindexptr and date_format(time,'%Y-%m-%d %T') between '"+FromDate+"'  and '"+ToDate+"' and st.level='"+myClass+"'";
        }


        if( !mySection.equals("0") && myClass.equals("0") && ( !(FDate.trim().compareTo("")==0) && !(TDate.trim().compareTo("")==0)    ) )
        {
            Query = "select st.rollno, concat(st.firstname,' ',st.midname,' ',st.lastname), st.level, st.section, st.rfidtag, sc.schoolname, sa.time, date_format(sa.time,'%T') from AAV.studentattendence sa, AAV.Students st, AAV.Schools sc where sa.studentindexptr=st.indexptr and sc.indexptr=st.schoolindexptr and date_format(time,'%Y-%m-%d %T') between '"+FromDate+"'  and '"+ToDate+"' st.section='"+mySection+"'";
        }


        if( !mySection.equals("0") && !myClass.equals("0") && ( !(FDate.trim().compareTo("")==0) && !(TDate.trim().compareTo("")==0)    ) )
        {
            Query = "select st.rollno, concat(st.firstname,' ',st.midname,' ',st.lastname), st.level, st.section, st.rfidtag, sc.schoolname, sa.time, date_format(sa.time,'%T') from AAV.studentattendence sa, AAV.Students st, AAV.Schools sc where sa.studentindexptr=st.indexptr and sc.indexptr=st.schoolindexptr and date_format(time,'%Y-%m-%d %T') between '"+FromDate+"'  and '"+ToDate+"' and st.section='"+mySection+"' and st.level='"+myClass+"'";
        }

这就是问题所在，当我添加另一个过滤器时，这些可能性会急剧增加，因此会产生更多的查询和处理。 为了通过 JAVA 或 MYSQL 有效地处理这个问题，必须有一种方法。

针对这种情况的通用 sql 语句？

一个处理多个输入查询的 JAVA 库？

某事或其他...

可以用尽可能少的代码来处理这种情况（考虑到可能会添加过滤器）？

Answer 1

解决了，经过一段时间的思考，我得出了一个解决方案。这是解决此问题的通用单一查询：

 if( mySection.equals("0") && myClass.equals("0") && ( FDate.trim().compareTo("")==0 || TDate.trim().compareTo("")==0    ) )
        {
        out.println("Note: Please provide valid filteration attributes. Atleast one filter is required.");
        return;
        }


        Query = "select st.rollno, concat(st.firstname,' ',st.midname,' ',st.lastname), st.level, st.section, st.rfidtag, sc.schoolname, sa.time, date_format(sa.time,'%T') from AAV.studentattendence sa, AAV.Students st, AAV.Schools sc where sa.studentindexptr=st.indexptr and sc.indexptr=st.schoolindexptr and ( '0'='"+mySection+"' or st.section='"+mySection+"') and ('0'='"+myClass+"' or st.level='"+myClass+"') and (  (' 00:00:00'='"+FromDate+"' and ' 23:59:59'='"+ToDate+"')  or (date_format(time,'%Y-%m-%d %T') between '"+FromDate+"'  and '"+ToDate+"' )  )";


executeQuery(Query);

当被视为表达式时，默认值解析为 true，在我的例子中为“0”，查询变得通用，我们可以根据需要添加尽可能多的过滤器子句。