如何确定获取的Java ResultSet是否为空？ [英] How to find out if a Java ResultSet obtained is empty?

问题描述

  Class.forName（org.sqlite.JDBC）; 
 Connection conn = 
 DriverManager.getConnection（jdbc：sqlite：userdata.db）; 
语句stat = conn.createStatement（）; 
 
 ResultSet rs = stat.executeQuery（SELECT * from table WHERE is_query_processed = 0;）; 
 
 int rowcount = rs.getRow（）; 
 System.out.println（Row count =+ rowcount）; // output 1 
 
 rs.first（）; //此语句生成异常
  

为什么会这样？

< div通常使用的模式如下：

  boolean empty = true; 
 while（rs.next（））{
 // ResultSet处理这里
 empty = false; 
} 
 
 if（empty）{
 //空结果集
} 
  

Class.forName("org.sqlite.JDBC");
Connection conn =
    DriverManager.getConnection("jdbc:sqlite:userdata.db");
Statement stat = conn.createStatement();

ResultSet rs = stat.executeQuery("SELECT * from table WHERE is_query_processed = 0;");

int rowcount = rs.getRow(); 
System.out.println("Row count = "+rowcount); // output 1

rs.first(); // This statement generates an exception

Why is it so?

解决方案

The pattern I normally use is as follows:

boolean empty = true;
while( rs.next() ) {
    // ResultSet processing here
    empty = false;
}

if( empty ) {
    // Empty result set
}

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