Java JDBC:查询返回单行时是否需要循环ResultSet? [英] Java JDBC: Do I need to loop ResultSet when query returns single row?

问题描述

我的sql查询仅返回一行.查询时，我需要遵循通常的while(rs.next) {...}模式还是可以:

My sql query returns one row only. When querying, do I need to follow the usual while(rs.next) {...} pattern or can I do:

...
rs.next();
int id  = rs.getInt("id");
int age = rs.getInt("age");
String first = rs.getString("first");
String last = rs.getString("last");
...

代替:

...
      while(rs.next()){
         //Retrieve by column name
         int id  = rs.getInt("id");
         int age = rs.getInt("age");
         String first = rs.getString("first");
         String last = rs.getString("last");
      }
...

推荐答案

没有，您不必每次都循环，因为rs.next()的调用已经将指针从null设置为第一个可用行并返回Wheather是否有条目.

No you don't have to loop every time since the call of rs.next() already sets the pointer from null to the first available row and returns wheather there is an entry or not.

检查所有返回的内容仍然有意义:

Still it makes sense to check if something was returned at all:

if(rs.next())
{
    // process resultset
}else
{
    // do something when no data arrived
}

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